3.13: Conclusion
We have now passed through the long course of India’s ancient and early medieval history. We began with the onset of India’s Neolithic period in the seventh millennium BCE and saw how India’s first civilization—the Harappan Civilization (2600 – 1700 BCE)—emerged from it in the northwestern region of the subcontinent during the third millennium BCE.
We then examined the long course of the Vedic Age (1700 – 600 BCE). As Harappan Civilization declined, Indo-Aryans migrated from Central Asia into northern India, bringing with them their Vedic religion, Sanskrit language, and pastoral and farming way of life. As they settled down on the Indo-Gangetic Plains and interacted with indigenous peoples, new political, social, and religious institutions formed. Over the course of several centuries, Aryan clan and tribal organization developed into kingdoms and oligarchies. Also, a simpler society composed of priests, warriors, and commoners evolved into a more complex society organized by varnas , the system of four hereditary social classes. Finally, the Vedic religion of the Brahmin priests evolved into Brahmanism, the earliest stage in the development of Hinduism.
Next, we surveyed a transitional period in India’s history that began in the sixth century and lasted until 321 BCE. Sixteen major kingdoms and oligarchies with roots in the late Vedic Age fought for control over territory in northern India. The kingdom of Magadha dominated. Accompanying this time of warring states, India entered a second stage of urbanization, as towns and cities became a prominent feature of the north. Alongside the varnas , the caste system began to form, organizing Indian society into a much larger number of social groups based on occupation, residence, language, and religious beliefs. Lastly, new religious ideas were put forward by the Buddha (c. 563 – 480 BCE) to challenge the dominance of Brahmanism, and Buddhist monastic communities began to form.
This transitional period ended when Chandragupta Maurya overthrew the last Magadhan dynasty in 321 BCE and established the Mauryan Empire (321 – 184 BCE). He and his successors built the first Indian state that included most of the subcontinent. Chandragupta’s grandson, King Ashoka (r. 268 – 232), is famed for having tried to rule this large realm according to Buddhist principles.
We then saw how, for five centuries after the fall of the Mauryan Empire (c. 200 BCE – 300 CE), no one major power ruled India. The entire subcontinent saw instead a fairly rapid turnover of regional monarchies. Some developed along the Ganges River, while others, such as the Kushan Kingdom, were of Central Asian origins. Also, states such as the Satavahana Kingdom formed in southern India. Yet, in spite of the political instability, India was economically dynamic, as trade within and without the subcontinent flourished, and India was increasingly linked to other parts of the world in such networks of exchange as the Silk Road and Indian Ocean maritime trade. Lastly, new trends appeared in Buddhism and Hinduism, most notably a popular, devotional form of worship.
Although India remained a mosaic of states during the period 300 – 600 BCE, historians recognize this time as distinct because the Gupta Empire (320 – 550 CE) included much of northern India and facets of Gupta period society and culture suggest that Indian civilization had matured and entered a classical age. One facet was individual achievements in literature, the arts, and sciences. But equally as important, the lives of all members of society were now being shaped and given meaning by a political pattern, social institutions, religious traditions, and a culture with a deep history. That political pattern included, for example, notions of kingship and the king’s dharma, as well as political hierarchy. Social institutions included the patriarchal family, varna and caste, and commercial associations in cities and towns. As for religious traditions, we have focused on the development of Hinduism and Buddhism and how they shaped the religious landscape with their long literary and scriptural traditions, notions of dharma, and monastic and temple life.
We ended this chapter by introducing early medieval India (c. 600 – 1300 BCE). The political scene remained one of powerful regional states, each with their unique local histories and traditions. The methods by which kings established relations with neighboring rulers and within their own lands has been described as Indian feudalism. Some kings, like the Cholas, buttressed their power by claiming to rule according to Hindu notions of dharma, by, for instance, building large Hindu temples and patronizing the Brahmins. Finally, during these centuries, Islamic rule, communities, and religion entered the South Asian landscape, changing the course of India’s history.


6.9: Introduction to the Recruitment Process
What you’ll learn to do: Discuss the recruitment process
The essence of recruiting is expressed in researcher, advisor and bestselling author Jim Collin’s classic recommendation: “get the right people on the bus.” This analogy, presented in his 2001 bestseller Good to Great , reflects the realities of operating in a dynamic and disruptive environment. [1] In the years since, this insight has been widely recognized as a critical business success factor. Recent economic, labor and technological trends have only increased the stakes. In this section, we’ll discuss the recruitment process and the importance of employer branding.
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Collins, Jim.
Good to Great.
New York, New York: Harper Collins, 2001. ↵


2.31: Languages
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- Susan Rahman, Prateek Sunder, and Dahmitra Jackson
- CC ECHO
In the United States, language learning is taught both inside and outside of the academy. An opportunity to learn a new language allows students to expand their horizons and increase their marketability in the workforce. Languages worldwide however, are more numerous than the selection that is represented by most community college offerings. It is a choice made by each institution to offer certain languages over others, which centers some as more valuable. While some of that has to do with the need for bilingual speakers in the workforce, particularly Spanish, there are numerous European languages taught more frequently than languages such as Cantonese or Arabic, demonstrating a Eurocentric prioritizing of language learning. Spanish and French are the most commonly taught languages in U.S.schools, privileging those as the preferred options for U.S. students. And even within these two dominant language offerings, we see a preference towards a preferred type of Spanish or French taught in schools rooted in the form spoken in Europe. In pragmatic terms this has more to do with where it came from than its practical application to those who may be speaking it.For the billions of Spanish speakers living in the Americas, their dialect is seen as not proper and instead what is known as Spain Spanish is the form of Spanish regarded by many instructors,professors, and educators as the more prestigious or appropriate Spanish to teach to language learners. For many indigenous Spanish speakers in the US, this type of Spanish is not what they speak at home. In many ways there is a hierarchy to the type of Spanish which is seen as better and it correlates directly to race, region, and ethnicity and the stigma surrounding the vernacular is evident. The closer the dialect is to the European Spanish brought to the Americas by the colonizers, the better.
So if you really want to hurt me, talk badly about my language. Ethnic Identity is twin skinned to linguistic identity-I am my language. Until I can take pride in my language, I cannot take pride in myself. Until I can accept as legitimate Chicano Texas Spanish, Tex-Mex and all the other languages I speak, I cannot accept the legitimacy of myself. Until I am free to write bilingually and to switch codes without having always to translate, while I still have to speak English or Spanish, when I would rather speak Spanglish, as long as I have to accommodate the English speakers rather than having them accommodate me, my tongue will be illegitimate (Anzaldúa, 2012 p. 81).
Disregarding dialects and linguistic difference as not the right way to speak is a form of privileging language to resemble that of the conquerors. Because of this, we see some of the more European nations in South America being privileged over the more indigenous ones.Argentinian Spanish is a close second to Spain’s Spanish in terms of favorability, but nations like Guatemala or various Caribbean nations whose Spanish departs from the conqueror’s Spanish in its usage is not often taught in US schools. Perhaps not coincidentally, these nations also have a majority population that is ethnically non-anglo-European. French too becomes privileged if it is rooted in the nation of France, while other colonized nations that France is spoken in are less valuable. So those who study French in school whose roots are Creole or from various African nations like Morocco, Algeria, or Senegal may not recognize what they are learning as what they know at home.
The United States was created as an English speaking country on land that already had inhabitants who spoke other languages. Despite this, there are almost no institutions of higher learning that offer any languages indigenous to the Americas such as Náhutal, Quechua, or Quichéas apart of their “foreign languages” offering. Some schools do offer introductions to select indigenous dialects through their school’s Native American Studies departments though they are few.
Students enter higher education with varied exposure to speaking and learning a second language in their earlier schooling. A student's experience with foreign language classes has alot to do with their race and social class, and the school system in which their K-12 education took place. “Black students at the K–12 level are more likely to attend schools or be tracked into programs in which foreign languages are not available” (Anya & Randolph, 2019). If a student is not offered an opportunity to learn early on, as they move into higher education,that area of learning often becomes more of an intimidating obligation, rather than something to get excited to learn more about. It also creates yet another field in higher education that is lacking representation. According to Musu-Gillete, et al., 2017, Black students in the U.S.“complete the least number of high school credits in this subject; they earn only 4% of bachelor’s degrees conferred in the field of foreign languages; and Black teachers comprise just 6% of instructors in the humanities and a mere 3% of postsecondary foreign language faculty” (Musu-Gillete, et al., 2017; U.S. Department of Education, 2016).
These statistics are not due to a low interest or lack of motivation on the part of Black students to learn language; rather, it can be traced back to past and current segregation, inequitable distribution of resources, and the systemic exclusion and marginalization of African Americans in U.S. schools (Glynn, 2012). Further, teacher perceptions of their students have long been shown to contribute to student success so when a teacher harbors unconscious bias favoring white students over students of color, the result is that students of color disproportionately suffer. In a 2012 study of “79 students analyzing experiences in foreign language study, and perceptions of the low enrollment of African-American students in foreign language classes,findings reflected that teachers and fellow students harbored negative perceptions and stereotypes of African-American students” (Glynn, 2012).
Using whiteness as a standard for imagery and teaching culture to students has also proven to be a way to leave swaths of students out. Representation matters and languages like Spanish are spoken all over the globe by people from many different ethnic backgrounds. Leaving those representations out of the teaching clearly hinders student success.
Black students could not see themselves in mainstream Spanish teaching materials. The images found in instructional materials were overwhelmingly of White Spanish speakers worldwide. The visuals omitted Afro-Hispanic history and Afro-Latinx presence not to mention the absence of other marginalized groups like the large Spanish-speaking Indigenous populations. After all, it may be easier for Black students to see themselves speaking Spanish if they see, hear, and learn about Afro-Cubans, the Spanish speakers of Equatorial Guinea, and multicultural Puerto Ricans, among others. My Black students helped me to dig deeper to develop and publish more inclusive and thought-provoking instructional materials to use with all of my students (Spaine Long, 2020).
So much of language learning is designed for non-native speakers. Perhaps until native speakers from nations that do not have the specific preferred form of their language traditionally taught in the US began studying language, there was not as much pushback on the fact that this preference exists, but for those who see their particular culture disregarded as insufficient, it becomes problematic.
The majority of language teaching in US schools comes with outrageously expensive textbooks, which many students just cannot afford. There is a reckoning with this in terms of some faculty decrying the prohibitive costs, and as mentioned above, privileging of languages of the conquerors, but roots run deep and change comes slow (Hines-Gaither, 2020). In fact,the American Council on the Teaching of Foreign Languages (ACTFL) has put together a list of Resources that Address Issues of Race,Diversity, and Social Justice , in order to address the need for change. ACTFL began in “1967 as a small offshoot of the Modern Language Association(MLA), and has set industry standards, established proficiency guidelines, advocated for language and education funding,” so like many of other discipline specific organizations, the ACTFL acted in response to the highly visible police murders of George Floyd, Breonna Taylor and so many unnamed other Black and Brown people in recent years (Resources that Address Issues of Race, Diversity, and Social Justice, n.d.). What comes from this depends on those in the field continuing to shine a light on the present inequity.


7.6: Rhetorical Devices
Rhetorical devices offer a way for speakers to arrange language in an artful way so as to make the conversation more engaging and subsequently, more memorable for audience members. Professional and amateur speech writers can employ any number of rhetorical devices to spice up the delivery of a presentation (see Table 7.1).
| Alliteration | Allusion | Anadiplosis | Analogy |
| Anaphora | Anesis | Antimetabole | Antithesis |
| Aposiopesis | Appositio | Assonance | Asyndeton |
| Catachresis | Climax | Conduplicatio | Diacope |
| Distinctio | Enthymeme | Enumeratio | Epanalepsis |
| Epistrophe | Epitheton | Epizeuxis | Eupemismos |
| Exemplum | Expletive | Hyperbole | Hypophora |
| Metaphor | Oxymoron | Paradox | Parallelism |
| Personification | Polysyndeton | Rhetorical Question | Scesis Onomaton |
| Sententia | Simile | Symploce | Synecdoche |
Greek and Roman scholars in the classical period developed and identified most rhetorical devices. Four of the most popular ones used in speeches include alliteration, antithesis, parallel structure, and repetition.
Home Alliteration
Alliteration occurs when the speaker uses the same letter or sound at the beginning of adjacent or closely connected words. Alliteration appears in everyday uses of language, such as television shows ( Mad Men ), sporting events (Final Four), company names (Dunkin Donuts), and in famous phrases (home sweet home; right as rain). When used sparingly, alliteration can spice up the language of delivery, such as “We owe it to our city to help the hungry, the homeless, and the helpless among us.” However, speakers can overuse alliteration, turning an otherwise innocuous statement into an exercise in pure silliness: “Nick’s nephew needed new notebooks now.”
Home Antithesis
The antithesis rhetorical technique juxtaposes two dissimilar or contrasting ideas. Consider President John F. Kennedy’s famous example: “ Ask not what your country can do for you—ask what you can do for your country .” Neil Armstrong used an antithesis as he took his first steps on the moon: “ That’s one small step for man, one giant leap for mankind .” Consider this technique when trying to draw attention to an important point. Other examples include:
- Many are called, but few are chosen.
- We are taught to speak, but rarely how to listen.
Home Parallel Structure and Repetition
Parallel structure uses the technique of arranging phrases or clauses of a sentence in parallel form, such as in the following examples:
- Dogs make great pets; they show loyalty, they show obedience, and they show love.
- Our coach told us we should get a lot of sleep, we should eat well, and we should think positively about tonight’s game.
Home Martin Luther King, Jr. masterfully used parallel structure and combined it with repetition to add engagement to his oratory. Consider his famous I Have a Dream speech :
I have a dream that one day this nation will rise up and live out the true meaning of its creed: “We hold these truths to be self-evident, that all men are created equal.”
I have a dream that one day on the red hills of Georgia, the sons of former slaves and the sons of former slave owners will be able to sit down together at the table of brotherhood.
I have a dream that one day even the state of Mississippi, a state sweltering with the heat of injustice, sweltering with the heat of oppression, will be transformed into an oasis of freedom and justice.
I have a dream that my four little children will one day live in a nation where they will not be judged by the color of their skin but by the content of their character.
I have a dream today!
Repetition occurs when the speaker repeats certain words or phrases to garner emotional effect. Those repeated phrases sound pleasant to the human ear, because they carry with them a certain rhythmic quality, adding emphasis and aiding in memory retention. Repetition as an element of public speaking works differently than it does in written communication. In public speaking, presenters should use repetition because it helps the audience remember key ideas. In written communication, repetition often gets avoided because a reader can review the original reference for memory and comprehension.


8.7.1: Viruses
No one knows exactly when viruses emerged or from where they came, since viruses do not leave historical footprints such as fossils. Modern viruses are thought to be a mosaic of bits and pieces of nucleic acids picked up from various sources along their respective evolutionary paths. Viruses are acellular, parasitic entities that are not classified within any domain because they are not considered alive. They have no plasma membrane, internal organelles, or metabolic processes, and they do not divide. Instead, they infect a host cell and use the host’s replication processes to produce progeny virus particles. Viruses infect all forms of organisms including bacteria, archaea, fungi, plants, and animals. Living things grow, metabolize, and reproduce. Viruses replicate, but to do so, they are entirely dependent on their host cells. They do not metabolize or grow, but are assembled in their mature form.
Figure \(\PageIndex{1}\): (a) The tobacco mosaic virus, seen by transmission electron microscopy, was the first virus to be discovered. (b) The leaves of an infected plant are shown. (credit a: scale-bar data from Matt Russell; credit b: modification of work by USDA, Department of Plant Pathology Archive, North Carolina State University)Viruses are diverse. They vary in their structure, their replication methods, and in their target hosts or even host cells. While most biological diversity can be understood through evolutionary history, such as how species have adapted to conditions and environments, much about virus origins and evolution remains unknown.
How Viruses Replicate
Viruses were first discovered after the development of a porcelain filter, called the Chamberland-Pasteur filter, which could remove all bacteria visible under the microscope from any liquid sample. In 1886, Adolph Meyer demonstrated that a disease of tobacco plants, tobacco mosaic disease, could be transferred from a diseased plant to a healthy one through liquid plant extracts. In 1892, Dmitri Ivanowski showed that this disease could be transmitted in this way even after the Chamberland-Pasteur filter had removed all viable bacteria from the extract. Still, it was many years before it was proven that these “filterable” infectious agents were not simply very small bacteria but were a new type of tiny, disease-causing particle.
Virions, single virus particles, are very small, about 20–250 nanometers (1 nanometer = 1/1,000,000 mm). These individual virus particles are the infectious form of a virus outside the host cell. Unlike bacteria (which are about 100 times larger), we cannot see viruses with a light microscope, with the exception of some large virions of the poxvirus family (Figure \(\PageIndex{2}\)).
Figure \(\PageIndex{2}\): The size of a virus is very small relative to the size of cells and organelles.It was not until the development of the electron microscope in the 1940s that scientists got their first good view of the structure of the tobacco mosaic virus (Figure \(\PageIndex{1}\)) and others. The surface structure of virions can be observed by both scanning and transmission electron microscopy, whereas the internal structures of the virus can only be observed in images from a transmission electron microscope (Figure \(\PageIndex{3}\)).
Figure \(\PageIndex{3}\): The ebola virus is shown here as visualized through (a) a scanning electron micrograph and (b) a transmission electron micrograph. (credit a: modification of work by Cynthia Goldsmith, CDC; credit b: modification of work by Thomas W. Geisbert, Boston University School of Medicine; scale-bar data from Matt Russell)The use of this technology has allowed for the discovery of many viruses of all types of living organisms. They were initially grouped by shared morphology, meaning their size, shape, and distinguishing structures. Later, groups of viruses were classified by the type of nucleic acid they contained, DNA or RNA, and whether their nucleic acid was single- or double-stranded. More recently, molecular analysis of viral replication cycles has further refined their classification.
A virion consists of a nucleic-acid core, an outer protein coating, and sometimes an outer envelope made of protein and phospholipid membranes derived from the host cell. The most visible difference between members of viral families is their morphology, which is quite diverse. An interesting feature of viral complexity is that the complexity of the host does not correlate to the complexity of the virion. Some of the most complex virion structures are observed in bacteriophages, viruses that infect the simplest living organisms, bacteria.
Viruses come in many shapes and sizes, but these are consistent and distinct for each viral family (Figure \(\PageIndex{4}\)). All virions have a nucleic-acid genome covered by a protective layer of protein, called a capsid. The capsid is made of protein subunits called capsomeres. Some viral capsids are simple polyhedral “spheres,” whereas others are quite complex in structure. The outer structure surrounding the capsid of some viruses is called the viral envelope. All viruses use some sort of glycoprotein to attach to their host cells at molecules on the cell called viral receptors. The virus exploits these cell-surface molecules, which the cell uses for some other purpose, as a way to recognize and infect specific cell types. For example, the measles virus uses a cell-surface glycoprotein in humans that normally functions in immune reactions and possibly in the sperm-egg interaction at fertilization. Attachment is a requirement for viruses to later penetrate the cell membrane, inject the viral genome, and complete their replication inside the cell.
The T4 bacteriophage, which infects the E. coli bacterium, is among the most complex virion known; T4 has a protein tail structure that the virus uses to attach to the host cell and a head structure that houses its DNA.
Adenovirus, a nonenveloped animal virus that causes respiratory illnesses in humans, uses protein spikes protruding from its capsomeres to attach to the host cell. Nonenveloped viruses also include those that cause polio (poliovirus), plantar warts (papillomavirus), and hepatitis A (hepatitis A virus). Nonenveloped viruses tend to be more robust and more likely to survive under harsh conditions, such as the gut.
Enveloped virions like HIV (human immunodeficiency virus), the causative agent in AIDS (acquired immune deficiency syndrome), consist of nucleic acid (RNA in the case of HIV) and capsid proteins surrounded by a phospholipid bilayer envelope and its associated proteins (Figure \(\PageIndex{4}\)). Chicken pox, influenza, and mumps are examples of diseases caused by viruses with envelopes. Because of the fragility of the envelope, nonenveloped viruses are more resistant to changes in temperature, pH, and some disinfectants than enveloped viruses.
Overall, the shape of the virion and the presence or absence of an envelope tells us little about what diseases the viruses may cause or what species they might infect, but is still a useful means to begin viral classification.
ART CONNECTION
Figure \(\PageIndex{4}\): Viruses can be complex in shape or relatively simple. This figure shows three relatively complex virions: the bacteriophage T4, with its DNA-containing head group and tail fibers that attach to host cells; adenovirus, which uses spikes from its capsid to bind to the host cells; and HIV, which uses glycoproteins embedded in its envelope to do so. Notice that HIV has proteins called matrix proteins, internal to the envelope, which help stabilize virion shape. HIV is a retrovirus, which means it reverse transcribes its RNA genome into DNA, which is then spliced into the host’s DNA. (credit “bacteriophage, adenovirus”: modification of work by NCBI, NIH; credit “HIV retrovirus”: modification of work by NIAID, NIH)Which of the following statements about virus structure is true?
- All viruses are encased in a viral membrane.
- The capsomere is made up of small protein subunits called capsids.
- DNA is the genetic material in all viruses.
- Glycoproteins help the virus attach to the host cell.
Unlike all living organisms that use DNA as their genetic material, viruses may use either DNA or RNA as theirs. The virus core contains the genome or total genetic content of the virus. Viral genomes tend to be small compared to bacteria or eukaryotes , containing only those genes that code for proteins the virus cannot get from the host cell. This genetic material may be single-stranded or double-stranded. It may also be linear or circular. While most viruses contain a single segment of nucleic acid, others have genomes that consist of several segments.
DNA viruses have a DNA core. The viral DNA directs the host cell’s replication proteins to synthesize new copies of the viral genome and to transcribe and translate that genome into viral proteins. DNA viruses cause human diseases such as chickenpox, hepatitis B, and some venereal diseases like herpes and genital warts.
RNA viruses contain only RNA in their cores. To replicate their genomes in the host cell, the genomes of RNA viruses encode enzymes not found in host cells. RNA polymerase enzymes are not as stable as DNA polymerases and often make mistakes during transcription. For this reason, mutations, changes in the nucleotide sequence, in RNA viruses occur more frequently than in DNA viruses. This leads to more rapid evolution and change in RNA viruses. For example, the fact that influenza is an RNA virus is one reason a new flu vaccine is needed every year. Human diseases caused by RNA viruses include hepatitis C, measles, and rabies.
Viruses can be seen as obligate intracellular parasites. The virus must attach to a living cell, be taken inside, manufacture its proteins and copy its genome, and find a way to escape the cell so the virus can infect other cells and ultimately other individuals. Viruses can infect only certain species of hosts and only certain cells within that host. The molecular basis for this specificity is that a particular surface molecule, known as the viral receptor, must be found on the host cell surface for the virus to attach. Also, metabolic differences seen in different cell types based on differential gene expression are a likely factor in which cells a virus may use to replicate. The cell must be making the substances the virus needs, such as enzymes the virus genome itself does not have genes for, or the virus will not be able to replicate using that cell.
Steps of Virus Infections
A virus must “take over” a cell to replicate. The viral replication cycle can produce dramatic biochemical and structural changes in the host cell, which may cause cell damage. These changes, called cytopathic effects, can change cell functions or even destroy the cell. Some infected cells, such as those infected by the common cold virus (rhinovirus), die through lysis (bursting) or apoptosis (programmed cell death or “cell suicide”), releasing all the progeny virions at once. The symptoms of viral diseases result from the immune response to the virus, which attempts to control and eliminate the virus from the body, and from cell damage caused by the virus. Many animal viruses, such as HIV (human immunodeficiency virus), leave the infected cells of the immune system by a process known as budding, where virions leave the cell individually. During the budding process, the cell does not undergo lysis and is not immediately killed. However, the damage to the cells that HIV infects may make it impossible for the cells to function as mediators of immunity, even though the cells remain alive for a period of time. Most productive viral infections follow similar steps in the virus replication cycle: attachment, penetration, uncoating, replication, assembly, and release.
A virus attaches to a specific receptor site on the host-cell membrane through attachment proteins in the capsid or proteins embedded in its envelope. The attachment is specific, and typically a virus will only attach to cells of one or a few species and only certain cell types within those species with the appropriate receptors.
CONCEPT IN ACTION
View this video for a visual explanation of how influenza attacks the body.
Unlike animal viruses, the nucleic acid of bacteriophages is injected into the host cell naked, leaving the capsid outside the cell. Plant and animal viruses can enter their cells through endocytosis , in which the cell membrane surrounds and engulfs the entire virus. Some enveloped viruses enter the cell when the viral envelope fuses directly with the cell membrane. Once inside the cell, the viral capsid is degraded and the viral nucleic acid is released, which then becomes available for replication and transcription.
The replication mechanism depends on the viral genome. DNA viruses usually use host cell proteins and enzymes to make additional DNA that is used to copy the genome or be transcribed to messenger RNA (mRNA), which is then used in protein synthesis. RNA viruses, such as the influenza virus, usually use the RNA core as a template for synthesis of viral genomic RNA and mRNA. The viral mRNA is translated into viral enzymes and capsid proteins to assemble new virions (Figure \(\PageIndex{5}\)). Of course, there are exceptions to this pattern. If a host cell does not provide the enzymes necessary for viral replication, viral genes supply the information to direct synthesis of the missing proteins. Retroviruses, such as HIV, have an RNA genome that must be reverse transcribed to make DNA, which then is inserted into the host’s DNA. To convert RNA into DNA, retroviruses contain genes that encode the virus-specific enzyme reverse transcriptase that transcribes an RNA template to DNA. The fact that HIV produces some of its own enzymes, which are not found in the host, has allowed researchers to develop drugs that inhibit these enzymes. These drugs, including the reverse transcriptase inhibitor AZT, inhibit HIV replication by reducing the activity of the enzyme without affecting the host’s metabolism.
The last stage of viral replication is the release of the new virions into the host organism, where they are able to infect adjacent cells and repeat the replication cycle. Some viruses are released when the host cell dies and other viruses can leave infected cells by budding through the membrane without directly killing the cell.
ART CONNECTION
Figure \(\PageIndex{5}\): In influenza virus infection, glycoproteins attach to a host epithelial cell. As a result, the virus is engulfed. RNA and proteins are made and assembled into new virions.Influenza virus is packaged in a viral envelope, which fuses with the plasma membrane. This way, the virus can exit the host cell without killing it. What advantage does the virus gain by keeping the host cell alive?
CONCEPT IN ACTION
Click through this tutorial on viruses to identify structures, modes of transmission, replication, and more.
Viruses and Disease
Viruses cause a variety of diseases in animals, including humans, ranging from the common cold to potentially fatal illnesses like meningitis (Figure \(\PageIndex{6}\)). These diseases can be treated by antiviral drugs or by vaccines, but some viruses, such as HIV, are capable of avoiding the immune response and mutating so as to become resistant to antiviral drugs.
Figure \(\PageIndex{6}\): Viruses are the cause of dozens of ailments in humans, ranging from mild illnesses to serious diseases. (credit: modification of work by Mikael Häggström)Vaccines for Prevention
While we do have limited numbers of effective antiviral drugs, such as those used to treat HIV and influenza, the primary method of controlling viral disease is by vaccination, which is intended to prevent outbreaks by building immunity to a virus or virus family. A vaccine may be prepared using weakened live viruses, killed viruses, or molecular subunits of the virus. In general, live viruses lead to better immunity, but have the possibility of causing disease at some low frequency. Killed viral vaccine and the subunit viruses are both incapable of causing disease, but in general lead to less effective or long-lasting immunity.
Weakened live viral vaccines are designed in the laboratory to cause few symptoms in recipients while giving them immunity against future infections. Polio was one disease that represented a milestone in the use of vaccines. Mass immunization campaigns in the U.S. in the 1950s (killed vaccine) and 1960s (live vaccine) essentially eradicated the disease, which caused muscle paralysis in children and generated fear in the general population when regional epidemics occurred. The success of the polio vaccine paved the way for the routine dispensation of childhood vaccines against measles, mumps, rubella, chickenpox, and other diseases.
Live vaccines are usually made by attenuation (weakening) of the “wild-type” (disease-causing) virus by growing it in the laboratory in tissues or at temperatures different from what the virus is accustomed to in the host. For example, the virus may be grown in cells in a test tube, in bird embryos, or in live animals. The adaptation to these new cells or temperature induces mutations in the virus’ genomes, allowing them to grow better in the laboratory while inhibiting their ability to cause disease when reintroduced into the conditions found in the host. These attenuated viruses thus still cause an infection, but they do not grow very well, allowing the immune response to develop in time to prevent major disease. The danger of using live vaccines, which are usually more effective than killed vaccines, is the low but significant risk that these viruses will revert back to their disease-causing form by back mutations. Back mutations occur when the vaccine undergoes mutations in the host such that it readapts to the host and can again cause disease, which can then be spread to other humans in an epidemic. This happened as recently as 2007 in Nigeria where mutations in a polio vaccine led to an epidemic of polio in that country.
Some vaccines are in continuous development because certain viruses, such as influenza and HIV, have a high mutation rate compared to other viruses or host cells. With influenza, mutation in genes for the surface molecules helps the virus evade the protective immunity that may have been obtained in a previous influenza season, making it necessary for individuals to get vaccinated every year. Other viruses, such as those that cause the childhood diseases measles, mumps, and rubella, mutate so little that the same vaccine is used year after year.
Vaccines and Antiviral Drugs for Treatment
In some cases, vaccines can be used to treat an active viral infection. In the case of rabies, a fatal neurological disease transmitted in the saliva of rabies virus-infected animals, the progression of the disease from the time of the animal bite to the time it enters the central nervous system may be two weeks or longer. This is enough time to vaccinate an individual who suspects being bitten by a rabid animal, and the boosted immune response from the vaccination is enough to prevent the virus from entering nervous tissue. Thus, the fatal neurological consequences of the disease are averted and the individual only has to recover from the infected bite. This approach is also being used for the treatment of Ebola, one of the fastest and most deadly viruses affecting humans, though usually infecting limited populations. Ebola is also a leading cause of death in gorillas. Transmitted by bats and great apes, this virus can cause death in 70–90 percent of the infected within two weeks. Using newly developed vaccines that boost the immune response, there is hope that immune systems of affected individuals will be better able to control the virus, potentially reducing mortality rates.
Another way of treating viral infections is the use of antiviral drugs. These drugs often have limited ability to cure viral disease but have been used to control and reduce symptoms for a wide variety of viral diseases. For most viruses, these drugs inhibit the virus by blocking the actions of one or more of its proteins. It is important that the targeted proteins be encoded for by viral genes and that these molecules are not present in a healthy host cell. In this way, viral growth is inhibited without damaging the host. There are large numbers of antiviral drugs available to treat infections, some specific for a particular virus and others that can affect multiple viruses.
Antivirals have been developed to treat genital herpes (herpes simplex II) and influenza. For genital herpes, drugs such as acyclovir can reduce the number and duration of the episodes of active viral disease during which patients develop viral lesions in their skins cells. As the virus remains latent in nervous tissue of the body for life, this drug is not a cure but can make the symptoms of the disease more manageable. For influenza, drugs like Tamiflu can reduce the duration of “flu” symptoms by one or two days, but the drug does not prevent symptoms entirely. Other antiviral drugs, such as Ribavirin, have been used to treat a variety of viral infections.
By far the most successful use of antivirals has been in the treatment of the retrovirus HIV, which causes a disease that, if untreated, is usually fatal within 10–12 years after being infected. Anti-HIV drugs have been able to control viral replication to the point that individuals receiving these drugs survive for a significantly longer time than the untreated.
Anti-HIV drugs inhibit viral replication at many different phases of the HIV replicative cycle. Drugs have been developed that inhibit the fusion of the HIV viral envelope with the plasma membrane of the host cell (fusion inhibitors), the conversion of its RNA genome to double-stranded DNA (reverse transcriptase inhibitors), the integration of the viral DNA into the host genome (integrase inhibitors), and the processing of viral proteins (protease inhibitors).
When any of these drugs are used individually, the virus’ high mutation rate allows the virus to rapidly evolve resistance to the drug. The breakthrough in the treatment of HIV was the development of highly active anti-retroviral therapy (HAART), which involves a mixture of different drugs, sometimes called a drug “cocktail.” By attacking the virus at different stages of its replication cycle, it is difficult for the virus to develop resistance to multiple drugs at the same time. Still, even with the use of combination HAART therapy, there is concern that, over time, the virus will evolve resistance to this therapy. Thus, new anti-HIV drugs are constantly being developed with the hope of continuing the battle against this highly fatal virus.
Summary
Viruses are acellular entities that can usually only be seen with an electron microscope. Their genomes contain either DNA or RNA, and they replicate using the replication proteins of a host cell. Viruses are diverse, infecting archaea, bacteria, fungi, plants, and animals. Viruses consist of a nucleic-acid core surrounded by a protein capsid with or without an outer lipid envelope.
Viral replication within a living cell always produces changes in the cell, sometimes resulting in cell death and sometimes slowly killing the infected cells. There are six basic stages in the virus replication cycle: attachment, penetration, uncoating, replication, assembly, and release. A viral infection may be productive, resulting in new virions, or nonproductive, meaning the virus remains inside the cell without producing new virions.
Viruses cause a variety of diseases in humans. Many of these diseases can be prevented by the use of viral vaccines, which stimulate protective immunity against the virus without causing major disease. Viral vaccines may also be used in active viral infections, boosting the ability of the immune system to control or destroy the virus. Antiviral drugs that target enzymes and other protein products of viral genes have been developed and used with mixed success. Combinations of anti-HIV drugs have been used to effectively control the virus, extending the lifespan of infected individuals.
Art Connections
Figure \(\PageIndex{4}\): Which of the following statements about virus structure is true?
A. All viruses are encased in a viral membrane.
B. The capsomere is made up of small protein subunits called capsids.
C. DNA is the genetic material in all viruses.
D. Glycoproteins help the virus attach to the host cell.
- Answer
-
D
Figure \(\PageIndex{5}\): Influenza virus is packaged in a viral envelope, which fuses with the plasma membrane. This way, the virus can exit the host cell without killing it. What advantage does the virus gain by keeping the host cell alive?
- Answer
-
The host cell can continue to make new virus particles.
Glossary
- acellular
- lacking cells
- apoptosis
- the cell death caused by induction of a cell’s own internal mechanisms either as a natural step in the development of a multicellular organism or by other environmental factors such as signals from cells of the immune system
- attenuation
- the weakening of a virus during vaccine development
- capsid
- the protein coating of the viral core
- cytopathic
- causing cell damage
- glycoprotein
- a protein molecule with attached carbohydrate molecules
- vaccine
- a weakened solution of virus components, viruses, or other agents that produce an immune response
- virion
- an individual virus particle outside a host cell
- viral envelope
- a lipid bilayer that envelops some viruses
Contributors and Attributions
-
Samantha Fowler (Clayton State University), Rebecca Roush (Sandhills Community College), James Wise (Hampton University). Original content by OpenStax (CC BY 4.0; Access for free at https://cnx.org/contents/b3c1e1d2-83...4-e119a8aafbdd ).


1.4: Add and Subtract Integers
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Learning Objectives
- Use negatives and opposites
- Simplify: expressions with absolute value
- Add integers
- Subtract integers
A more thorough introduction to the topics covered in this section can be found in the Prealgebra chapter, Integers .
Use Negatives and Opposites
Our work so far has only included the counting numbers and the whole numbers. But if you have ever experienced a temperature below zero or accidentally overdrawn your checking account, you are already familiar with negative numbers. Negative numbers are numbers less than \(0\). The negative numbers are to the left of zero on the number line. See Figure \(\PageIndex{1}\).
The arrows on the ends of the number line indicate that the numbers keep going forever. There is no biggest positive number, and there is no smallest negative number.
Is zero a positive or a negative number? Numbers larger than zero are positive, and numbers smaller than zero are negative. Zero is neither positive nor negative.
Consider how numbers are ordered on the number line. Going from left to right, the numbers increase in value. Going from right to left, the numbers decrease in value. See Figure \(\PageIndex{2}\).
Doing the Manipulative Mathematics activity “Number Line-part 2” will help you develop a better understanding of integers.
Remember that we use the notation:
\(a \lt b\) (read “\(a\) is less than \(b\)”) when \(a\) is to the left of \(b\) on the number line.
\(a \gt b\) (read “\(a\) is greater than \(b\)”) when \(a\) is to the right of \(b\) on the number line.
Now we need to extend the number line which showed the whole numbers to include negative numbers, too. The numbers marked by points in Figure \(\PageIndex{3}\). are called the integers. The integers are the numbers \(...−3, −2, −1, 0, 1, 2, 3…\)
Example \(\PageIndex{1}\)
Order each of the following pairs of numbers, using \(<\) or \(>\):
- \(14 \; \_\_\_\; 6\)
- \(-1\; \_\_\_ \;9\)
- \(-1\; \_\_\_ -4\)
- \(\;\; 2 \;\_\_\_ -20\)
Solution :
It may be helpful to refer to the number line shown.
Figure \(\PageIndex{4}\)
\( \begin{align*}1. \quad & 14\;\_\_\_\;6 \\[4pt]
& 14 > 6 && \text{\(14\) is to the right of \(6\) on the number line.} \\[8pt]
2. \quad & -1\;\_\_\_\;9 \\[4pt]
& -1 < 9 && \text{\(-1\) is to the left of \(9\) on the number line.}\\[8pt]
3. \quad & -1\;\_\_\_-4 \\[4pt]
& -1 > -4 && \text{\(-1\) is to the right of \(-4\) on the number line.}\\[8pt]
4. \quad & 2\;\_\_\_-20 \\[4pt]
& 2 > -20 && \text{\(2\) is to the right of \(-20\) on the number line.}\
\end{align*} \)
Try It \(\PageIndex{1}\)
Order each of the following pairs of numbers, using \(<\) or \(>\):
- \(15 \; \_\_\_\; 7\)
- \(-2 \; \_\_\_\; 5\)
- \(-3 \; \_\_\_\; -7\)
- \(5 \; \_\_\_\; -17\)
- Answer
-
- \(<\)
- \(>\)
- \(<\)
- \(>\)
Try It \(\PageIndex{2}\)
Order each of the following pairs of numbers, using \(<\) or \(>\):
- \(8 \; \_\_\_\; 13\)
- \(3 \; \_\_\_\; -4\)
- \(-5 \; \_\_\_\; -2\)
- \(9 \; \_\_\_\; -21\)
- Answer
-
- \(<\)
- \(>\)
- \(<\)
- \(>\)
You may have noticed that, on the number line , the negative numbers are a mirror image of the positive numbers, with zero in the middle. Because the numbers \(2\) and \(−2\) are the same distance from zero, they are called opposite s . The opposite of \(2\) is \(−2\), and the opposite of \(−2\) is \(2\).
OPPOSITE
The opposite of a number is the number that is the same distance from zero on the number line but on the opposite side of zero.
Figure \(\PageIndex{5}\) illustrates the definition.
Sometimes in algebra the same symbol has different meanings. Just like some words in English, the specific meaning becomes clear by looking at how it is used. You have seen the symbol “\(−\)” used in three different ways.
\[\begin{align*} &10 − 4 \quad \text{Between two numbers, it indicates the operation of }\textit{subtraction}.\\ & \qquad \qquad \text{We read } 10 - 4 \, \text{as “}10 \, \text{minus} \, 4.\text{”}\\[5pt]
&-8 \quad \text{In front of a number, it indicates a }\textit{negative}\text{ number.}\\ & \qquad \qquad \text{We read} -8 \text{ as “negative eight.”}\\[5pt]
&-x \quad \text{In front of a variable, it indicates the }\textit{opposite.} \\ & \qquad \qquad \text{We read } -x \text{ as “the opposite of } x\text{”}\\[5pt]
&-(-2) \quad \text{Here there are two “−” signs.}\\
& \qquad \qquad \text{The one in the parentheses tells us the number is negative }2. \\
& \qquad \qquad \text{ The one outside the parentheses tells us to take the }\textit{opposite}\text{ of }−2. \\
& \qquad \qquad \text{ We read }−(−2) \text{ as “the opposite of negative two.”} \end{align*}\]
OPPOSITE NOTATION
\(−a\) means the opposite of the number \(a\).
The notation \(−a\) is read as “the opposite of \(a\).”
Example \(\PageIndex{2}\)
Find:
- the opposite of \(7\)
- the opposite of \(−10\)
- the opposite of \(−(−6)\)
Solution :
1.\( \quad −7\) is the same distance from \(0\) as \(7\), but on the opposite side of \(0\). The opposite of \(7\) is \(-7\).
2.\( \quad 10\) is the same distance from \(0\) as \(−10\), but on the opposite side of \(0\). The opposite of \(-10\) is \(10\).
3. \(\quad\)The opposite of \(-(-6)\) is \(-6\).
Try It \(\PageIndex{3}\)
Find:
- the opposite of \(4\)
- the opposite of \(−3\)
- \(−(−1)\)
- Answer
-
- \(-4\)
- \(3\)
- \(1\)
Try It \(\PageIndex{4}\)
Find:
- the opposite of \(8\)
- the opposite of \(−5\)
- \(−(−5)\)
- Answer
-
- \(-8\)
- \(5\)
- \(5\)
Our work with opposites gives us a way to define the integers. The whole numbers and their opposites are called the integers . The integers are the numbers \(…−3,−2,−1,0,1,2,3…\)
INTEGERS
The whole numbers and their opposites are called the integers .
The integers are the numbers
\[…−3,−2,−1,0,1,2,3… \nonumber \]
When evaluating the opposite of a variable , we must be very careful. Without knowing whether the variable represents a positive or negative number, we don’t know whether −x−x is positive or negative. We can see this in Example \(\PageIndex{1}\).
Example \(\PageIndex{3}\):
Evaluate
- \(-x\), when \(x = 8\)
- \(-x\), when \(x = -8\)
Solution :
-
-x Write the opposite of 8. -8 -
-x Write the opposite of -8. 8
Try It \(\PageIndex{5}\)
Evaluate \(-n\), when
- \(n = 4\)
- \(n = -4\)
- Answer
-
- \(-4\)
- \(4\)
Try It \(\PageIndex{6}\)
Evaluate \(-m\), when
- \(m = 11\)
- \(m = -11\)
- Answer
-
- \(-11\)
- \(11\)
Simplify: Expressions with Absolute Value
We saw that numbers such as \(2\) and \(−2\) are opposites because they are the same distance from \(0\) on the number line. They are both two units from \(0\). The distance between \(0\) and any number on the number line is called the absolute value of that number.
ABSOLUTE VALUE
The absolute value of a number is its distance from \(0\) on the number line.
The absolute value of a number \( n \) is written as \(|n|\).
For example,
- \(−5\) is \(5\) units away from \(0\), so \(|−5|=5\).
- \(5\) is \(5\) units away from \(0\), so \(|5|=5\).
Figure \(\PageIndex{6}\) illustrates this idea.
The absolute value of a number is never negative (because distance cannot be negative). The only number with absolute value equal to zero is the number zero itself, because the distance from \(0\) to \(0\) on the number line is zero units.
PROPERTY OF ABSOLUTE VALUE
\(|n| \geq 0\) for all numbers
Absolute values are always greater than or equal to zero!
Mathematicians say it more precisely, “absolute values are always non-negative.” Non-negative means greater than or equal to zero.
Example \(\PageIndex{4}\):
Simplify:
- \(|3|\)
- \(|-44|\)
- \(|0|\)
Solution :
The absolute value of a number is the distance between the number and zero. Distance is never negative, so the absolute value is never negative.
- \( |3| = 3\)
- \(|-44| = 44\)
- \( |0| = 0\)
Try It \(\PageIndex{7}\)
Simplify:
- \(|4|\)
- \(|-28|\)
- \(|0|\)
- Answer
-
- \(4\)
- \(28\)
- \(0\)
Try It \(\PageIndex{8}\)
Simplify:
- \(|-13|\)
- \(|47|\)
- Answer
-
- \(13\)
- \(47\)
In the next example, we’ll order expressions with absolute values. Remember, positive numbers are always greater than negative numbers!
Example \(\PageIndex{5}\):
Fill in \(<, >, \text{or} =\) for each of the following pairs of numbers:
- \(|−5| \; {\underline{\hspace {2 em}}} \;−|−5|\)
- \(8 \;{\underline{\hspace {2 em}}} \;−|−8|\)
- \(-9 \;{\underline{\hspace {2 em}}} \;−|−9|\)
- \(-(-16) \;{\underline{\hspace {2 em}}}\; −|−16|\)
Solution :
-
\(\begin{array} {llll} {\text{Simplification}} &{|-5|} & {\underline{\hspace {2 em}}} &{-|-5|} \\ {\text{Order.}} &{5} &{\underline{\hspace {2 em}}} &{-5} \\ {} &{5} &{>} &{-5} \\ {} &{|-5|} &{>} &{-|-5|} \\ \end{array}\) -
\(\begin{array} {llll} {\text{Simplification}} &{8} & {\underline{\hspace {2 em}}} &{-|-8|} \\ {\text{Order.}} &{8} &{\underline{\hspace {2 em}}} &{-8} \\ {} &{8} &{>} &{-8} \\ \text{so }\\ {} & {|8|} &{>} &{-|-8|} \\ \end{array}\) -
\(\begin{array} {llll} {\text{Simplification}} &{-9} & {\underline{\hspace {2 em}}} &{-|-9|} \\ {\text{Order.}} &{-9} &{\underline{\hspace {2 em}}} &{-9} \\ {} &{-9} &{=} &{-9} \\ \text{so } \\ {} & {-9} &{=} &{-|-9|} \\ \end{array}\) -
\(\begin{array} {llll} {\text{Simplification}} &{-(-16)} & {\underline{\hspace {2 em}}} &{-|16|} \\ {\text{Order.}} &{16} &{\underline{\hspace {2 em}}} &{-16} \\ {} &{16} &{>} &{-16} \\ \text{so } \\ {} & {-(-16)} &{>} &{-|-16|} \\ \end{array}\)
Try It \(\PageIndex{9}\)
Fill in \(<, >, \text{or} =\) for each of the following pairs of numbers:
- \(|−9| \;{\underline{\hspace {2 em}}} \; −|−9|\)
- \(2 \;{\underline{\hspace {2 em}}} \; −|−2|\)
- \(-8 \;{\underline{\hspace {2 em}}} \; −|−8|\)
- \(-(-9) \;{\underline{\hspace {2 em}}} \; −|−9|\)
- Answer
-
- \(>\)
- \(>\)
- \(<\)
- \(>\)
Try It \(\PageIndex{10}\)
Fill in \(<, >, \text{or} =\) for each of the following pairs of numbers:
- \(7 \;{\underline{\hspace {2 em}}} \; −|−7|\)
- \(-(-10) \;{\underline{\hspace {2 em}}} \; −|−10|\)
- \(|-4| \;{\underline{\hspace {2 em}}} \; −|−4|\)
- \(-1 \;{\underline{\hspace {2 em}}} \; |−1|\)
- Answer
-
- \(>\)
- \(>\)
- \(>\)
- \(<\)
We now add absolute value bars to our list of grouping symbols. When we use the order of operations, first we simplify inside the absolute value bars as much as possible, then we take the absolute value of the resulting number.
GROUPING SYMBOLS
\[\begin{array} {llll} {\text{Parentheses}} &{()} & {\text{Braces}} & {\{\}} \\ {\text{Brackets}} &{[\space]} &{\text{Absolute}} &{|\space|} \\ \end{array} \nonumber\]
In the next example, we simplify the expressions inside absolute value bars first, just like we do with parentheses.
Example \(\PageIndex{6}\):
Simplify: \(24 - |19 - 3(6 - 2)|\)
Solution :
\[\begin{array} {ll} {} &{24 - |19 - 3(6 - 2)|} \\ {\text{Work inside parentheses first: subtract } 2\space \text{from } 6} &{24 - |19 - 3(4)|} \\ {\text{Multiply }3(4)} &{24 - |19 - 12|} \\ {\text{Subtract inside the absolute value bars. }} &{24 - |7|} \\ {\text{Take the absolute value.}} &{24 - 7} \\ {\text{Subtract.}} &{17} \end{array}\nonumber\]
Try It \(\PageIndex{11}\)
Simplify: \(19 - |11 - 4(3 - 1)|\)
- Answer
-
\(16\)
Try It \(\PageIndex{12}\)
Simplify: \(9 - |8 - 4(7 - 5)|\)
- Answer
-
\(9\)
Example \(\PageIndex{7}\)
Evaluate:
- \(|x|\) when \(x = -35\)
- \(|y|\) when \(y = -20\)
- \(-|u|\) when \(u = 12\)
- \(-|p|\) when \(p = -14\)
Solution :
1. \(|x|\) when \(x = -35\)
\(\begin{array} {ll} {} &{|x|} \\ {\text{Substitute } -35 \space \text{for }x} &{|-35|} \\ {\text{Take the absolute value.}} &{35} \end{array}\)
2. \(|y|\) when \(y = -20\)
\(\begin{array} {ll} {} &{|-y|} \\ {\text{Substitute } -20 \space \text{for }y} &{|-(-20)|} \\ {\text{Simplify}} &{|20|} \\ {\text{Take the absolute value.}} &{20} \end{array}\)
3. \(-|u|\) when \(u = 12\)
\(\begin{array} {ll} {} &{-|u|} \\ {\text{Substitute } 12 \space \text{for }u} &{|-12|} \\ {\text{Take the absolute value.}} &{-12} \end{array}\)
4. \(-|p|\) when \(p = -14\)
\(\begin{array} {ll} {} &{-|p|} \\ {\text{Substitute } -14 \space \text{for }p} &{-|-14|} \\ {\text{Take the absolute value.}} &{-14} \end{array}\)
Try It \(\PageIndex{13}\)
Evaluate:
- \(|x|\) when \(x = -17\)
- \(|y|\) when \(y = -39\)
- \(-|m|\) when \(m = 22\)
- \(-|p|\) when \(p = -11\)
- Answer
-
- \(17\)
- \(39\)
- \(-22\)
- \(-11\)
Try It \(\PageIndex{14}\)
Evaluate:
- \(|y|\) when \(y = -23\)
- \(|-y|\) when \(y = -21\)
- \(-|n|\) when \(n = 37\)
- \(-|q|\) when \(q = -49\)
- Answer
-
- \(23\)
- \(21\)
- \(-37\)
- \(-49\)
Add Integers
Most students are comfortable with the addition and subtraction facts for positive numbers. But doing addition or subtraction with both positive and negative numbers may be more challenging.
Doing the Manipulative Mathematics activity “Addition of Signed Numbers” will help you develop a better understanding of adding integers.”
We will use two color counters to model addition and subtraction of negatives so that you can visualize the procedures instead of memorizing the rules.
We let one color (blue) represent positive. The other color (red) will represent the negatives. If we have one positive counter and one negative counter, the value of the pair is zero. They form a neutral pair. The value of this neutral pair is zero.
We will use the counters to show how to add the four addition facts using the numbers \(5, −5\) and \(3,−3\).
\[\begin{array} {llll} {5 + 3} &{-5 + (-3)} &{-5 + 3} &{5 + (-3)} \end{array} \nonumber \]
To add \(5+3\), we realize that \(5+3\) means the sum of \(5\) and \(3\).
| We start with \(5\) positives. | |
| And then we add \(3\) positives. | |
| We now have \(8\) positives. The sum of \(5\) and \(3\) is \(8\). |
Now we will add \(−5 + (−3)\). Watch for similarities to the last example \(5 + 3 = 8\).
To add \(−5 + (−3)\), we realize this means the sum of \(−5\) and \(−3\).
| We start with \(5\) negatives. | |
| And then we add \(3\) negatives. | |
| We now have \(8\) negative. The sum of \(-5\) and \(-3\) is \(-8\). |
In what ways were these first two examples similar?
- The first example adds \(5\) positives and \(3\) positives—both positives.
- The second example adds \(5\) negatives and \(3\) negatives—both negatives.
In each case we got \(8\) — either \(8\) positives or \(8\) negatives.
When the signs were the same, the counters were all the same color, and so we added them.
Example \(\PageIndex{8}\)
Add:
- \(1 + 4\)
- \(-1 + (-4)\)
Solution :
1.
\(1\) positive plus \(4\) positives is \(5\) positives.
2.
\(1\) negative plus \(4\) negatives is \(5\) negatives.
Try It \(\PageIndex{15}\)
Add:
- \(2 + 4\)
- \(-2 + (-4)\)
- Answer
-
- \(6\)
- \(-6\)
Try It \(\PageIndex{16}\)
Add:
- \(2 + 5\)
- \(-2 + (-5)\)
- Answer
-
- \(7\)
- \(-7\)
So what happens when the signs are different? Let’s add \(−5+3\). We realize this means the sum of \(−5\) and \(3\). When the counters were the same color, we put them in a row. When the counters are a different color, we line them up under each other.
| \(-5 + 3\) means the sum of \(-5\) and \(3\). | |
| We start with \(5\) negatives. | |
| And then we add \(3\) positives. | |
| We remove any neutral pairs. | |
| We have \(2\) negatives left. | |
| The sum of \(-5\) and \(3\) is \(-2\). | \(-5 + 3 = 2\) |
Notice that there were more negatives than positives, so the result was negative.
Let’s now add the last combination, \(5+(−3)\).
| \(5 + (-3)\) means the sum of \(-5\) and \(-3\). | |
| We start with \(5\) positives. | |
| And then we add \(3\) negatives. | |
| We remove any neutral pairs. | |
| We have \(2\) positives left. | |
| The sum of \(5\) and \(-3\) is \(2\). | \(5 + (-3) = 2\) |
When we use counters to model addition of positive and negative integers, it is easy to see whether there are more positive or more negative counters. So we know whether the sum will be positive or negative.
Example \(\PageIndex{9}\)
Add:
- \(-1 + 5\)
- \(1 + (-5)\)
Solution :
1. \(-1 + 5\)
There are more positives, so the sum is positive.
So, \(-1 + 5 = 4\).
2. \(1 + (-5)\)
There are more negatives, so the sum is negative.
So, \(1 + (-5) = -4\)
Try It \(\PageIndex{17}\)
Add:
- \(-2 + 4\)
- \(2 + (-4)\)
- Answer
-
- \(2\)
- \(-2\)
Try It \(\PageIndex{18}\)
Add:
- \(-2 + 5\)
- \(2 + (-5)\)
- Answer
-
- \(3\)
- \(-3\)
Now that we have added small positive and negative integers with a model, we can visualize the model in our minds to simplify problems with any numbers.
When you need to add numbers such as \(37+(−53)\), you really don’t want to have to count out \(37\) blue counters and \(53\) red counters. With the model in your mind, can you visualize what you would do to solve the problem?
Picture \(37\) blue counters with \(53\) red counters lined up underneath. Since there would be more red (negative) counters than blue (positive) counters, the sum would be negative . How many more red counters would there be? Because \(53−37=16\), there are \(16\) more red counters.
Therefore, the sum of \(37+(−53)\) is \(−16\).
\[37+(−53)=−16\nonumber\]
Let’s try another one. We’ll add \(−74+(−27)\). Again, imagine \(74\) red counters and \(27\) more red counters, so we’d have \(101\) red counters. This means the sum is \(−101\).
\[−74+(−27)=−101\nonumber\]
Let’s look again at the results of adding the different combinations of \(5,−5\) and \(3, -3\).
ADDITION OF POSITIVE AND NEGATIVE INTEGERS
\[\begin{array} {ll} {5 + 3=8} &{-5 + (-3)=-8} \\{\text{both positive, sum positive}} &{\text{both negative, sum negative}} \end{array}\nonumber\]
When the signs are the same, the counters would be all the same color, so add them.
\[\begin{array} {ll} {-5 + 3=-2} &{5 + (-3)=2} \\{\text{different signs, more negatives, sum negative}} &{\text{different signs, more positives, sum positive}} \end{array}\nonumber\]
When the signs are different, some of the counters would make neutral pairs, so subtract to see how many are left.
Visualize the model as you simplify the expressions in the following examples.
Example \(\PageIndex{10}\)
Simplify:
- \(19 + (-47)\)
- \(-14 + (-36)\)
Solution :
1. Since the signs are different, we subtract \(19\) from \(47\). The answer will be negative because there are more negatives than positives.
\(\text{Add.} \qquad 19 + (-47) = -28\)
2. Since the signs are same, we add. The answer will be negative because there are more negatives than positives.
\(\text{Add.} \qquad-14 + (-36) = -50\)
Try It \(\PageIndex{19}\)
Simplify:
- \(-31 + (-19)\)
- \(15 + (-32)\)
- Answer
-
- \(-50\)
- \(-17\)
Try It \(\PageIndex{20}\)
Simplify:
- \(-42 + (-28)\)
- \(25 + (-61)\)
- Answer
-
- \(-70\)
- \(-36\)
The techniques used up to now extend to more complicated problems, like the ones we’ve seen before. Remember to follow the order of operations!
Example \(\PageIndex{11}\)
Simplify:
\(-5 + 3(-2 + 7)\)
Solution :
\[\begin{array} {ll} {} &{-5 + 3(-2 + 7)} \\ {\text{Simplify inside the parenthesis}} &{-5 + 3(5)} \\{\text{Multiply}} &{-5 + 15} \\{\text{add left to right}} &{10} \end{array}\nonumber\]
Try It \(\PageIndex{21}\)
Simplify:
\(-2 + 5(-4 + 7)\)
- Answer
-
\(13\)
Try It \(\PageIndex{22}\)
Simplify:
\(-4 + 2(-3 + 5)\)
- Answer
-
\(0\)
Subtract Integers
Note
Doing the Manipulative Mathematics activity “Subtraction of Signed Numbers” will help you develop a better understanding of subtracting integers.
We will continue to use counters to model the subtraction. Remember, the blue counters represent positive numbers and the red counters represent negative numbers.
Perhaps when you were younger, you read “\(5−3\)” as “\(5\) take away \(3\).” When you use counters, you can think of subtraction the same way!
We will model the four subtraction facts using the numbers \(5\) and \(3\).
\[\begin{array} {llll} {5 - 3} &{-5 - (-3))} &{-5 -3} &{5 - (-3)} \end{array}\nonumber\]
To subtract \(5−3\), we restate the problem as “\(5\) take away \(3\).”
| We start with \(5\) positives. | |
| We 'take away' \(3\) positives. | |
| We have \(2\) positives left. | |
| The difference of \(5\) and \(3\) is \(2\). | \(2\) |
Now we will subtract \(−5−(−3)\). Watch for similarities to the last example \(5−3=2\).
To subtract \(−5−(−3)\), we restate this as “\(–5\) take away \(–3\)”
| We start with \(5\) negatives. | |
|
We 'take away' \(3\) negatives. |
|
| We have \(2\) negatives left. | |
| The difference of \(-5\) and \(-3\) is \(-2\). |
\(-2\) |
Notice that these two examples are much alike: The first example, we subtract 3 positives from 5 positives and end up with 2 positives.
In the second example, we subtract 3 negatives from 5 negatives and end up with 2 negatives.
Each example used counters of only one color, and the “take away” model of subtraction was easy to apply.
Example \(\PageIndex{12}\)
Subtract:
- \(7 - 5\)
- \(-7 - (-5)\)
Solution :
- \[\begin{array} {ll} {7 - 5} \\ {2}&{\text{Take }5\space \text{positives from }7 \space \text{positives and get }2\space \text{positives}} & \end{array}\nonumber\]
- \[\begin{array} {ll} {-7 - (-5)} \\ {-2} &{\text{Take }5\space \text{negatives from }7 \space \text{negatives and get }2\space \text{negatives}} \end{array}\nonumber\]
Try It \(\PageIndex{23}\)
Subtract:
- \(6 - 4\)
- \(-6 - (-4)\)
- Answer
-
- \(2\)
- \(-2\)
Try It \(\PageIndex{24}\)
Subtract:
- \(7 - 4\)
- \(-7 - (-4)\)
- Answer
-
- \(3\)
- \(-3\)
What happens when we have to subtract one positive and one negative number? We’ll need to use both white and red counters as well as some neutral pairs . Adding a neutral pair does not change the value. It is like changing quarters to nickels—the value is the same, but it looks different.
- To subtract \(−5−3\), we restate it as \(−5\) take away \(3\).
We start with \(5\) negatives. We need to take away \(3\) positives, but we do not have any positives to take away.
Remember, a neutral pair has value zero. If we add \(0\) to \(5\) its value is still \(5\). We add neutral pairs to the \(5\) negatives until we get \(3\) positives to take away.
| \(-5 -3\) means \(-5\) take away \(3\) | |
| We start with \(5\) negatives. | |
| We now add the neutrals needed to get \(3\) positives. | |
| We remove the \(3\) positives. | |
| We are left with \(8\) negatives. | |
| The difference of \(-5\) and \(3\) is \(-8\). | \(-5 - 3 = -8\) |
And now, the fourth case, \(5−(−3)\). We start with \(5\) positives. We need to take away \(3\) negatives, but there are no negatives to take away. So we add neutral pairs until we have \(3\) negatives to take away.
| \(5 -(-3)\) means \(5\) take away \(-3\) | |
| We start with \(5\) positives. | |
| We now add the needed neutrals pairs. | |
| We remove the \(3\) negatives. | |
| We are left with \(8\) positives. | |
| The difference of \(5\) and \(-3\) is \(8\). | \(5 - (-3) = 8\) |
Example \(\PageIndex{13}\)
Subtract:
- \(-3 -1\)
- \(3 - (-1)\)
Solution :
1.
|
Take 1 positive from the one added neutral pair. |
|
\(\begin{array} {l} {-3 -1} \\ {-4} \end{array}\) |
|
Take 1 negative from the one added neutral pair. |
|
\(\begin{array} {l} {3 - (-1)} \\ {4} \end{array}\) |
Try It \(\PageIndex{25}\)
Subtract:
- \(-6 -4\)
- \(6 - (-4)\)
- Answer
-
- \(-10\)
- \(10\)
Try It \(\PageIndex{26}\)
Subtract:
- \(-7-4\)
- \(7 - (-4)\)
- Answer
-
- \(-11\)
- \(11\)
Have you noticed that subtraction of signed numbers can be done by adding the opposite ? In Exercise \(\PageIndex{33}\), \(−3−1\) is the same as \(−3+(−1)\) and \(3−(−1)\) is the same as \(3+1\). You will often see this idea, the subtraction property , written as follows:
SUBTRACTION PROPERTY
\[a−b=a+(−b) \nonumber\]
Subtracting a number is the same as adding its opposite.
Look at these two examples.
Of course, when you have a subtraction problem that has only positive numbers, like \(6−4\), you just do the subtraction. You already knew how to subtract \(6−4\) long ago. But knowing that \(6−4\) gives the same answer as \(6+(−4)\) helps when you are subtracting negative numbers. Make sure that you understand how \(6−4\) and \(6+(−4)\) give the same results!
Example \(\PageIndex{14}\)
Simplify:
- \(13 - 8 \space \text{and } 13 + (-8)\)
- \(-17 - 9 \space \text{and } -17 + (-9)\)
Solution :
- \(\begin{array} {llll} {\text{Subtract.}} &{13 - 8} &{\text{and}} &{13 + (-8)} \\ {} &{5} &{} &{5} \end{array}\)
- \(\begin{array} {llll} {\text{Subtract.}} &{-17 - 9} &{\text{and}} &{-17 + (-9)} \\ {} &{-26} &{} &{-26} \end{array}\)
Try It \(\PageIndex{27}\)
Simplify:
- \(21 - 13 \space \text{and } 21 + (-13)\)
- \(-11 - 7 \space \text{and } -11 + (-7)\)
- Answer
-
- \(8\)
- \(-18\)
Try It \(\PageIndex{28}\)
Simplify:
- \(15 - 7 \space \text{and } 15 + (-7)\)
- \(-14 - 8 \space \text{and } -14 + (-8)\)
- Answer
-
- \(8\)
- \(-22\)
Look at what happens when we subtract a negative.
Subtracting a negative number is like adding a positive!
You will often see this written as \(a−(−b)=a+b\).
Does that work for other numbers, too? Let’s do the following example and see.
Example \(\PageIndex{15}\)
Simplify:
- \(9 - (-15) \space \text{and } 9 + 15\)
- \(-7 - (-4) \space \text{and } -7 + 4\)
Solution :
- \(\begin{array} {lll} {} &{9 - (-15)} &{9 + 15} \\ {\text{Subtract}} &{24} &{24} \end{array}\)
- \(\begin{array} {lll} {} &{-7 - (-4)} &{-7 + 4} \\ {\text{Subtract}} &{-3} &{-3} \end{array}\)
Try It \(\PageIndex{29}\)
Simplify:
- \(6 - (-13) \space \text{and } 6 + 13\)
- \(-5 - (-1) \space \text{and } -5 + 1\)
- Answer
-
- \(19\)
- \(-4\)
Try It \(\PageIndex{30}\)
Simplify:
- \(4 - (-19) \space \text{and } 4 + 19\)
- \(-4 - (-7) \space \text{and } -4 + 7\)
- Answer
-
- \(23\)
- \(3\)
Let’s look again at the results of subtracting the different combinations of \(5,−5\) and \(3,−3\).
SUBTRACTION OF INTEGERS
\[\begin{array} {l} {5 - 3} &{-5 - (-3)} \\ {2} &{-2} \\ {5\space\text{positives take away }3\space\text{positives}} &{5\space\text{negatives take away }3\space\text{negatives}} \\ {2\space\text{positives}} &{2\space\text{negatives}} \end{array}\nonumber\]
When there would be enough counters of the color to take away, subtract.
\[\begin{array} {l} {-5 - 3} &{5 - (-3)} \\ {-8} &{8} \\ {5\space\text{negatives, want to take away }3\space\text{positives}} &{5\space\text{positives, want to take away }3\space\text{negatives}} \\ {\text{need neutral pairs}} &{\text{need neutral pairs}} \end{array}\nonumber\]
When there would be not enough counters of the color to take away, add.
What happens when there are more than three integers? We just use the order of operations as usual.
Example \(\PageIndex{16}\)
Simplify:
\(7 - (-4 -3) - 9\)
Solution :
\[ \begin{array} {ll} {} &{7 - (-4 - 3) - 9} \\ {\text{Simplify inside the parenthesis first.}} &{7 - (-7) - 9} \\ {\text{Subtract left to right.}} &{14 - 9} \\ {\text{Subtract}} &{5} \end{array}\nonumber\]
Try It \(\PageIndex{31}\)
Simplify:
\(8−(−3−1)−9\)
- Answer
-
\(3\)
Try It \(\PageIndex{32}\)
Simplify:
\(12−(−9−6)−14\)
- Answer
-
\(12\)
Access these online resources for additional instruction and practice with adding and subtracting integers. You will need to enable Java in your web browser to use the applications.
Key Concepts
- Addition of Positive and Negative Integers
\[\begin{array} {ll} {5 + 3} &{-5+(-3)} \\ {8} &{-8} \\ {\text{both positive,}} &{\text{both negative,}} \\ {\text{sum positive}} &{\text{sum negative}} \end{array}\nonumber\]
\[\begin{array} {ll} {-5 + 3} &{5+(-3)} \\ {-2} &{2} \\ {\text{different signs,}} &{\text{different signs,}} \\ {\text{more negatives}} &{\text{more positives}} \\ {\text{sum negative}} &{\text{sum positive}} \end{array}\nonumber\]
- Property of Absolute Value :
\(|n| \geq 0\) for all numbers. Absolute values are always greater than or equal to zero!
- Subtraction of Integers
\[\begin{array} {ll} {5 - 3} &{-5-(-3)} \\ {2} &{-2} \\ {5\space\text{positives}} &{5\space\text{negatives}} \\ {\text{take away 3 positives}} &{\text{take away 3 negatives}} \\ {\text{2 positives}} &{\text{2 negatives}} \end{array}\nonumber\]
\[\begin{array} {ll} {-5 - 3} &{5-(-3)} \\ {-8} &{8} \\ {\text{5 negatives, want to}} &{\text{5 positives, want to}} \\ {\text{subtract 3 positives}} &{\text{subtract 3 negatives}} \\ {\text{need neutral pairs}} &{\text{need neutral pairs}}\end{array}\nonumber\]
- Subtraction Property: Subtracting a number is the same as adding its opposite.
Glossary
- absolute value
- The absolute value of a number is its distance from 0 on the number line. The absolute value of a number nn is written as |n|.
- integers
- The whole numbers and their opposites are called the integers: \(...−3, −2, −1, 0, 1, 2, 3...\)
- opposite
- The opposite of a number is the number that is the same distance from zero on the number line but on the opposite side of zero: −\(a\) means the opposite of the number. The notation −\(a\) is read “the opposite of \(a\).”


12.E: Modern Applications of Microbial Genetics (Exercises)
12.1: Microbes and the Tools of Genetic Engineering
The science of using living systems to benefit humankind is called biotechnology. Technically speaking, the domestication of plants and animals through farming and breeding practices is a type of biotechnology. However, in a contemporary sense, we associate biotechnology with the direct alteration of an organism’s genetics to achieve desirable traits through the process of genetic engineering.
Multiple Choice
Which of the following is required for repairing the phosphodiester backbone of DNA during molecular cloning?
- cDNA
- reverse transcriptase
- restriction enzymes
- DNA ligase
- Answer
-
D
All of the following are processes used to introduce DNA molecules into bacterial cells except :
- transformation
- transduction
- transcription
- conjugation
- Answer
-
C
The enzyme that uses RNA as a template to produce a DNA copy is called:
- a restriction enzyme
- DNA ligase
- reverse transcriptase
- DNA polymerase
- Answer
-
C
In blue-white screening, what do blue colonies represent?
- cells that have not taken up the plasmid vector
- cells with recombinant plasmids containing a new insert
- cells containing empty plasmid vectors
- cells with a non-functional lacZ gene
- Answer
-
C
The T i plasmid is used for introducing genes into:
- animal cells
- plant cells
- bacteriophages
- E. coli cells
- Answer
-
B
True/False
Recombination is a process not usually observed in nature.
- Answer
-
false
It is generally easier to introduce recombinant DNA into prokaryotic cells than into eukaryotic cells.
- Answer
-
true
Fill in the Blank
The process of introducing DNA molecules into eukaryotic cells is called ________.
- Answer
-
transfection
Short answer
Name three elements incorporated into a plasmid vector for efficient cloning.
When would a scientist want to generate a cDNA library instead of a genomic library?
What is one advantage of generating a genomic library using phages instead of plasmids?
Critical Thinking
Is biotechnology always associated with genetic engineering? Explain your answer.
Which is more efficient: blunt-end cloning or sticky-end cloning? Why?
12.2: Visualizing and Characterizing DNA
Finding a gene of interest within a sample requires the use of a single-stranded DNA probe labeled with a molecular beacon (typically radioactivity or fluorescence) that can hybridize with a complementary single-stranded nucleic acid in the sample. Agarose gel electrophoresis allows for the separation of DNA molecules based on size. Restriction fragment length polymorphism (RFLP) analysis allows for the visualization by agarose gel electrophoresis of distinct variants of a DNA sequence.
Multiple Choice
Which technique is used to separate protein fragments based on size?
- polyacrylamide gel electrophoresis
- Southern blot
- agarose gel electrophoresis
- polymerase chain reaction
- Answer
-
A
Which technique uses restriction enzyme digestion followed by agarose gel electrophoresis to generate a banding pattern for comparison to another sample processed in the same way?
- qPCR
- RT-PCR
- RFLP
- 454 sequencing
- Answer
-
C
All of the following techniques involve hybridization between single-stranded nucleic acid molecules except :
- Southern blot analysis
- RFLP analysis
- northern blot analysis
- microarray analysis
- Answer
-
B
Fill in the Blank
The __________ blot technique is used to find an RNA fragment within a sample that is complementary to a DNA probe.
- Answer
-
northern
The PCR step during which the double-stranded template molecule becomes single-stranded is called _____________.
- Answer
-
denaturation
The sequencing method involving the incorporation of ddNTPs is called __________.
- Answer
-
Sanger sequencing, dideoxy method, or chain termination method
True/False
In agarose gel electrophoresis, DNA will be attracted to the negative electrode.
- Answer
-
false
Short answer
Why is it important that a DNA probe be labeled with a molecular beacon?
When separating proteins strictly by size, why is exposure to SDS first required?
Why must the DNA polymerase used during PCR be heat-stable?
Critical Thinking
Suppose you are working in a molecular biology laboratory and are having difficulty performing the PCR successfully. You decide to double-check the PCR protocol programmed into the thermal cycler and discover that the annealing temperature was programmed to be 65 °C instead of 50 °C, as you had intended. What effects would this mistake have on the PCR reaction? Refer to Figure 12.2.8 .
What is the advantage of microarray analysis over northern blot analysis in monitoring changes in gene expression?
What is the difference between reverse transcriptase PCR (RT-PCR) and real-time quantitative PCR (qPCR)?
12.3: Whole Genome Methods and Industrial Applications
Advances in molecular biology have led to the creation of entirely new fields of science. Among these are fields that study aspects of whole genomes, collectively referred to as whole-genome methods. In this section, we provide a brief overview of the whole-genome fields of genomics, transcriptomics, and proteomics.
Multiple Choice
The science of studying the entire collection of mRNA molecules produced by cells, allowing scientists to monitor differences in gene expression patterns between cells, is called:
- genomics
- transcriptomics
- proteomics
- pharmacogenomics
- Answer
-
B
The science of studying genomic fragments from microbial communities, allowing researchers to study genes from a collection of multiple species, is called:
- pharmacogenomics
- transcriptomics
- metagenomics
- proteomics
- Answer
-
C
The insulin produced by recombinant DNA technology is
- a combination of E. coli and human insulin.
- identical to human insulin produced in the pancreas.
- cheaper but less effective than pig insulin for treating diabetes.
- engineered to be more effective than human insulin.
- Answer
-
B
Fill in the Blank
The application of genomics to evaluate the effectiveness and safety of drugs on the basis of information from an individual’s genomic sequence is called ____________.
- Answer
-
pharmacogenomics or toxicogenomics
A gene whose expression can be easily visualized and monitored is called a ________.
- Answer
-
reporter gene
True/False
RNA interference does not influence the sequence of genomic DNA.
- Answer
-
true
Short answer
If all cellular proteins are encoded by the cell’s genes, what information does proteomics provide that genomics cannot?
Critical Thinking
What are some advantages of cloning human genes into bacteria to treat human diseases caused by specific protein deficiencies?
12.4: Genetic Engineering - Risks, Benefits, and Perceptions
Many types of genetic engineering have yielded clear benefits with few apparent risks. However, many emerging applications of genetic engineering are much more controversial, often because their potential benefits are pitted against significant risks, real or perceived. This is certainly the case for gene therapy, a clinical application of genetic engineering that may one day provide a cure for many diseases but is still largely an experimental approach to treatment.
Multiple Choice
At what point can the FDA halt the development or use of gene therapy?
- on submission of an IND application
- during clinical trials
- after manufacturing and marketing of the approved therapy
- all of the answers are correct
- Answer
-
D
Fill in the Blank
_____________ is a common viral vector used in gene therapy for introducing a new gene into a specifically targeted cell type.
- Answer
-
Adenovirus
Short Answer
Briefly describe the risks associated with somatic cell gene therapy.
Critical Thinking
Compare the ethical issues involved in the use of somatic cell gene therapy and germ-line gene therapy.


2.1: Definition and Information Asymmetry
The International Accounting Standards Board (IASB) has stated that the purpose of financial reporting is "to provide financial information about the reporting entity that is useful to existing and potential investors, lenders and other creditors in making decisions about providing resources to the entity. Those decisions involve buying, selling or holding equity and debt instruments, providing or settling loans and other forms of credit, or exercising rights to vote on, or otherwise influence, management's actions that affect the use of the entity's economic resources." (International Accounting Standards Board, 2019). The key elements of this definition are that information must be useful and that it must assist in the decision-making function. Although this primary definition identifies investors, lenders, and creditors as the user groups, the IASB does acknowledge that other users may also find financial statements useful. The IASB also acknowledges two key characteristics of the financial-reporting environment. First, most users, such as shareholders or lenders, do not have the ability to access information directly from the reporting entity. Thus, those users must rely on general-purpose financial statements as well as other sources to obtain the information. Second, management of the company has access to more information than the external users, as they can access internal, nonpublic sources from the company's records. These two conditions result in information asymmetry , which is a key concept in understanding the purpose and development of accounting standards.
Information asymmetry simply means that one individual has more information than another individual. This concept is very easy to understand and is obviously true in all kinds of interactions that occur in your life on a daily basis. When you enter the room to write an exam, you know how much sleep you had the night before and what you ate for breakfast, but your professor does not. This type of information advantage is not very useful to you, however, as your professor is interested only in what you write on your exam paper, not the conditions that led up to those responses. In other cases, however, it is possible that you could gain an information advantage that could be useful to your performance on the exam. In the broader perspective of financial accounting, we are concerned the implications and problems that may be caused by information asymmetry. To explore this concept further, we need to consider two different forms of information asymmetry: adverse selection and moral hazard .
Adverse selection occurs because employees and managers of a company have more knowledge of the company's operations than the general public and, more specifically, investors. Because these individuals know more about the company and its potential future profitability, they may be tempted to take advantage of this knowledge. For example, if a manager of a company knew that a contract had just been signed with a new customer that was going to significantly increase revenues in the following year, the manager may be tempted to purchase shares of the company on the open market before the contract is announced to the public. By doing so, the manager may benefit when the news of the contract is released and the price of the share rises. In this case, the manager has unfairly used his or her information advantage to gain a personal benefit, which can be considered adverse to the interests of other investors. Because investors are aware of this potential problem, they may lose confidence in the securities market. This could result in investors generally paying less for shares than may be warranted by the fundamental factors of the business. The investors would do this because they wouldn't completely trust the information they were receiving. If this lack of confidence became serious or widespread, it is possible that securities markets wouldn't function at all.
The field of financial accounting clearly has a role in trying to solve the adverse selection problem. By making sufficient, high-quality information available to investors in a timely manner, accountants can reduce the adverse effects of this form of information asymmetry. However, it is impossible to eliminate the problem completely, as insiders of a company will always receive the information first. The accounting profession must thus work toward cost-effective and reasonable (but imperfect) solutions to convey useful information to investors.
Moral hazard is a different type of problem caused by an information imbalance. Except for very small businesses, most companies operate under the principle of separation of ownership and management. Shareholders can be numerous and geographically diverse; it is impossible for them to be directly involved in the running of the business. To solve this problem, shareholders hire managers to act as stewards of their investment. One feature of corporate law is the presumption that managers will always work toward the best interests of the company. Shareholders assume this to be true, but they do not have a very effective method of directly observing manager behaviour. Managers know this; thus, there may be an incentive – or at least an opportunity – not to work as hard or as effectively as the shareholders would like. If the company's performance suffers because of poor manager effort, the manager can always blame outside factors or other economic conditions. In extreme cases, the manager may even be tempted to manipulate financial reports to cover up poor performance.
To give shareholders the ability to monitor manager performance, financial accounting must seek ways to provide financial performance measures. Many analytical techniques use financial accounting as a basis for the calculations. However, shareholders must have confidence not only in the accuracy of the information but also in the usefulness of the information for evaluation of management stewardship. Again, there is no perfect solution here, as the complexities and qualitative features of management activity can never be perfectly captured by numbers alone. Still, financial accounting information can help investors assess the quality of the managers they hire, which can potentially reduce the moral hazard problem.


16.21: Cancer and Gene Regulation - Cancer and Transcriptional Control
- Explain the role of transcription factors in cancer
Cancer and Transcriptional Control
Many transcription factors, especially some that are proto-oncogenes or tumor suppressors, help regulate the cell cycle and, as such, determine how large a cell will get and when it can divide into two daughter cells. Alterations in cells that give rise to cancer can affect the transcriptional control of gene expression. Mutations that activate transcription factors, such as increased phosphorylation, can increase the binding of a transcription factor to its binding site in a promoter. This could lead to increased transcriptional activation of that gene that results in modified cell growth. Alternatively, a mutation in the DNA of a promoter or enhancer region can increase the binding ability of a transcription factor. This could also lead to the increased transcription and aberrant gene expression that is seen in cancer cells.
Researchers have been investigating how to control the transcriptional activation of gene expression in cancer. Identifying how a transcription factor binds, or a pathway that activates where a gene can be turned off, has led to new drugs and new ways to treat cancer. In breast cancer, for example, many proteins are overexpressed. This can lead to increased phosphorylation of key transcription factors that increase transcription. One such example is the overexpression of the epidermal growth factor receptor (EGFR) in a subset of breast cancers. The EGFR pathway activates many protein kinases that, in turn, activate many transcription factors that control genes involved in cell growth. New drugs that prevent the activation of EGFR have been developed and are used to treat these cancers.
Key Points
- The mutations that activate transcription factors can increase the binding of a transcription factor to its binding site in a promoter leading to increased transcriptional activation of that gene and resulting in altered cell growth.
- A mutation in the DNA of a promoter or enhancer region may increase the binding ability of a transcription factor, which may then lead to the increased transcription and anomalous gene expression that is seen in cancer cells.
- Studying how to control the transcriptional activation of gene expression in cancer cells along with identifying how a transcription factor binds or a pathway activates where a gene can be turned off has led researchers to new drugs and novel ways of treating cancer.
Key Terms
- transcription factor : a protein that binds to specific DNA sequences, thereby controlling the flow (or transcription) of genetic information from DNA to mRNA


23.4: Game-Based Learning Examples
-
- Last updated
- Save as PDF
To move from theory into practice, some concrete examples show how games are being used for learning from K–12 through university and professional training levels.
- Educational Games Central: A pioneer in the use of computer-based games for learning, the Carrefour virtuel du jeux éducatifs, operated by the SAVIE research centre at the Université du Québec à Montréal, has recently been translated into English as Educational Games Central (EGC). The site (www.savie.qc .ca/carrefourjeux/an/accueil.htm) provides “frame games”—generic frameworks for well-known board games and game-show contests (e.g., Tic Tac Toe, Trivial Pursuit, Concentration, Snakes and Ladders) into which questions, problems, answers, and feedback can be entered to create specific games in any content area. Because each game shell is designed to let a teacher produce a game in an hour or two (once the content is developed), EGC can be used in the classroom or in a training context without extensive training or infrastructure. Its games are accessed on the Internet by individual players or teams; the newly released ENJEUX multiplayer environment (http:// www.savie.ca/enjeux) supports their use for multiple players online at different sites. Performance and research statistics can be collected for each play session. Although EGC games are based on more traditional question-and-answer exercises, they have proved very successful in using play and competition to engage learners from young children to adults. EGC games have recently been used for several health-related applications as part of the SAGE for Learning research project (www.sageforlearning .ca) on games and simulations for learning.
- COTS games in the schools: Commercial off-theshelf (referred to as COTS) games have being applied in many learning contexts. In one example, a school in the US reports using Roller Coaster Tycoon projects to teach momentum, speed, mass, and other concepts in junior-high physics classes (Kirremuir, 2006a). In another case, SimCity is being used for a complex Grade 6 to 8 project to create and manage a small city’s infrastructure and environmental impact (Kirriemuir, 2006b). In a third example, the Education Arcade project at MIT used Civilization III to teach high school and middle school social studies. The researchers found that students used much more complex concepts than expected. One student commented, “What I learned is that you can’t separate economics from politics or geography. What natural resources I have or where I’m located affects how I can negotiate with other civilizations.” (Jenkins & Squire, 2003).
- University, adult and professional learning: A project at Purdue University is building the Critical Mass video game to teach university chemistry through an adventure mission that requires solving chemistry problems (web.ics.purdue.edu/~kmartine/). Virtual-U (www.virtual-u.org/) lets players experience the intricacies of university management. Public Health Games (www.publichealth games.com/), a centre at the University of Illinois at Chicago, is creating “state of the art games for public health workers and emergency responders for a multitude of catastrophic scenarios,” including an anthrax attack response simulation. The Objection! simulation ( http://www.objection.com/ ), customizable for any state’s legal system, is used in US law schools to teach trial skills and is approved for continuing legal education.
- Mobile games: Naismith et al. (2004) use case studies to review how a number of mobile games implement current learning theories. One example is Environmental Detectives ( http://education.mit.edu/ar/ed .html), an augmented reality game, in which Grade 5 to 8 students use a constructivist approach, playing the role of environmental engineers searching for data to solve problems related to a toxic chemical spill. Simulation events are triggered by real-world locations as players navigate through a physical space.
Note
Search the Internet to find examples for your discipline. Some sites to start you off are the FutureLab showcase ( http://www.futurelab.org.uk/showcase /show.htm), BBC Schools ( http://www.bbc.co.uk /schools/games/), FunBrain.com (www.fun brain.com/), and the EDUCAUSE Games and Simulations page (www.educause.edu/Games andSimulations/11263).