5.9: The Power of Networking
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There is some wisdom in the saying that it’s who you know that brings success in getting a job. Consider the following:
- It is estimated that only 20 percent of new jobs and vacancies are advertised or posted.
- A Web posting for a job typically yields over 150 applicants for a position.
- Sixty to eighty percent of jobs are found through personal contact and networking.
What exactly is networking? In its simplest terms, it is the process of engaging others in helping you reach an objective. Three words in this definition deserve a closer look:
- Process. Networking is something that doesn’t happen casually but requires thought, planning, and deliberate activity.
- Engaging. You are looking to have others do something for you—give you information, guidance, other contacts, or perhaps a recommendation.
- Objective. You need to be clear about your purpose for networking—it is not merely to collect people’s contact information but to further your career development.
The process of networking involves three basic phases: prospect identification and management, making contact, and follow-up.
Student FAQs
- I won’t graduate and be in the job market for a couple years. Do I need to work on résumés and networking now? Yes, absolutely! Even though you aren’t yet graduating from college, there are many benefits to starting now. As a student, you are likely to be applying for part-time jobs, internships, and even volunteer positions. Networking is a process of building relationships, and the strongest relationships are built over time. Having a good network will help identify interesting and relevant opportunities. Having a résumé that summarizes your strengths and skills will give you an advantage over other candidates who apply without a résumé, because job application forms rarely give the opportunity to highlight your strengths. Furthermore, a résumé is an updated record of your skills and experience; it makes sense to capture your accomplishments as they happen and will save you a lot of time in the future.
- I don’t have any work experience. How can I write a résumé? You may not have any work experience, but you do have experience and skills. Focus on your transferable skills, and list examples of how you have used them. Think of organizations you have been involved in and volunteer work you have done. It is OK to include high school accomplishments; you can replace them with college accomplishments as you gain them. It is also OK to include your GPA, particularly if it is over 3.0, because that helps show you are disciplined and organized.
All Contacts Are Equal, but Some Are More So Than Others
The first phase involves identifying whom you should be speaking to and pinpointing the people who can introduce you to them. This is like the game Six Degrees of Kevin Bacon applied to your own life. Whom do you need to speak to? That really depends on your objectives. If you are trying to learn about an occupation, it can be just about anyone involved with that field. If you are in the process of trying to land an internship or a job, you want to reach the person who will make the hiring decision.
Your objective also defines how you get started with your networking. In the first case, you might want to start with people you met at an industry conference; in the job-specific case, you’ll want to think about whom you know in that company or who might know someone in that company. If you don’t have any contacts who fit that description, whom do you know who lives in the town in which the company is based or in a nearby town?
Your success in this phase of networking will be driven by the quality of the candidates (those who can directly influence your ability to reach your objectives) as well as the quantity (those who will lead you to the most contacts). This is why there is no such thing as a bad contact.
As important as having contacts is your ability to access those contacts when you need to. That is where contact management comes into play. Don’t be caught wishing you could call someone you met three weeks ago…if you could only remember what you did with their business card! There are countless ways to keep track of contacts, from writing names in an address book, to keeping a Rolodex, to using a computer-based contact management system. Choose a system you feel comfortable with—comfortable enough to use regularly. A sophisticated system that has all the bells and whistles is no good to you if you can’t use it.
Let technology help you in this endeavor. Your computer, PDA, or smartphone probably has features for capturing contact information and retrieving it based on keywords, and most will even connect with your calendar for scheduling and reminders. Consider Web-based applications such as those offered by SuccessHawk (www.successhawk.com) and networking sites focused on professional networking, such as LinkedIn. Whatever your choices, invest the time to learn to use them well; you’ll be very glad you did.
Building a network requires consistent work, and a strong network will take time to achieve. That is why we recommend you start building your professional network now—even early in your college career. Your network should include anyone who might have a connection that will help: family, friends, neighbors, past and present coworkers, bosses, people you met through associations and clubs (especially business associations), alumni from your college, and acquaintances you have met via online networking.
When you capture your contact data, use relevant keywords to help you search your database and shape your contact activity. One of the most overlooked pieces of information that you should be sure to capture is the source of the contact. That’s what turns a “cold call” into a “warm call”—and it helps engage the prospect. If a friend introduced you, be sure to note that friend’s name; if you met at a party, note the name of the host and the occasion; if you met at a conference, note the conference and date. You should also use other keywords so that you can quickly find the contacts that will be most effective for each of your objectives; keywords might describe the area of specialization, organization membership, or type of contact (family, friend, colleague, etc.).
Personal Contact
Being in the right place at the right time has much less to do with luck than with the art of personal contact. Contacts are everywhere, and you don’t know when you might turn one to your advantage. You may feel a little awkward following these tips at first, but with practice you will become quite adept at meeting new people and adding them to your network.
- Be prepared. If you are going to a conference, a party, or even a class, know ahead of time which people or kinds of people you want to meet. Be prepared with topics you can steer your contact toward so you don’t spend two minutes awkwardly talking about the weather and then slink away.
- Be confident. Prepare and learn a short introduction for yourself. Be factual, don’t brag, and give enough information about yourself to prompt your contact to ask questions.
- Be curious. The best way to get contacts to want to know you is to show you want to know them. Observe them before you step up to them. Is there something unique about them, the way they are dressed, or perhaps what you may have overheard that you can ask about? “I couldn’t help but notice that lovely necklace; is that from a local designer?” or “You have such an interesting accent; do you mind if I ask where you’re from?” After you ask the question, listen actively to keep the conversation going.
- Be prepared (part 2). Have a good supply of personal cards to give out to contacts; that will prompt them to give you their contact information, too. You don’t have to be in business to have “business cards.”
- Be courteous. If someone you know comes up to you while you are speaking with a contact, introduce them; if you see that the contact is getting antsy, tell them you enjoyed meeting them and then move on. Don’t trap them!
- Be prepared (part 3). Set yourself up for networking success by discreetly writing a word or two on the back of their card to jog your memory in the future. “World-class rodeo clown” will certainly help you remember who Jack Smith at Triangle Financial was.
Make the Call
What you say in your networking calls or e-mails will depend largely on the objective of your networking effort. (Is it to learn about an occupation or industry? Seek a job-shadowing opportunity? Ask for a job?) But some networking basics and elements of etiquette apply to all contacts:
- Be mindful of your contact’s time. Keep your calls and e-mails courteous but brief. If you are calling, ask if it is a good time to talk.
- If this is a first contact, tell the contact where you got his or her name. “I was referred to you by our friend Janet Smith” or “My colleague Richard Stewart suggested I call you” or “I heard you speak at the International Genius Conference” (remember the contact source information in your contact database?). This turns an interrupting cold call into a warm call with an interested individual.
- Be specific about how the contact can help you. Know what you are asking for and do so directly. Don’t be shy.
- Use your network for more than just asking for jobs. It is a great vehicle for learning about new trends in the industry, for launching “trial balloons” for ideas or concepts you are developing, and for seeking advice on practical aspects of your occupation.
- Help others in your network. Networking is not a one-way endeavor. Be willing to offer your assistance whenever you can; the fact that you are still in college doesn’t mean you can’t be of value. You may be able to get an introduction to an instructor for a person in the industry or help that person’s daughter learn about your college.
Care and Feeding of Your Network
Much of the success of your networking efforts depends on what you do after you’ve hung up after a call or received an e-mail reply. The first step is to thank your contact for his or her help. Do this right away; any thank-you after twenty-four hours of your contact can be considered late. Find a reason (not just an excuse) to keep in touch with people in your network. If you read an article people in your network would be interested in, send them the link. If you run across a problem one of your contacts might help you with, don’t be shy—give him or her a call to ask for help . If you meet someone you think a contact would like, make introductions. Send a follow-up note of thanks to a person who gave you a particularly productive lead. Let him or her know what you were able to accomplish. People like to know they are on a successful team. Finally, if a person in your network asks you for help, do what you say you will do .
Key Takeaways
- Networking is an ongoing process that involves identifying and managing prospects, making contact, and following up.
- All contacts are good contacts.
- Common courtesy and follow-through are the catalysts of good networking.
Checkpoint Exercises
- Give yourself twenty minutes to list one hundred people you know. (You may want to think of groups first and then see how quickly you can draw up the list.) Now give yourself another twenty minutes to write one or two words next to each name to describe how he or she could help you network.
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List three things you should do whenever you contact someone for the first time.
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Describe two things you can do to overcome shyness and network effectively in a person-to-person setting.
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12.1: Introduction to Finite Sampling Models
Basic Theory
Sampling Models
Suppose that we have a population \(D\) of \(m\) objects. The population could be a deck of cards, a set of people, an urn full of balls, or any number of other collections. In many cases, we simply label the objects from 1 to \(m\), so that \(D = \{1, 2, \ldots, m\}\). In other cases (such as the card experiment), it may be more natural to label the objects with vectors. In any case, \(D\) is usually a finite subset of \(\R^k\) for some \(k \in \N_+\).
Our basic experiment consists of selecting \(n\) objects from the population \(D\) at random and recording the sequence of objects chosen. Thus, the outcome is \(\bs{X} = (X_1, X_2, \ldots, X_n)\) where \(X_i \in D\) is the \(i\)th object chosen. If the sampling is with replacement , the sample size \(n\) can be any positive integer. In this case, the sample space \(S\) is \[ S = D^n = \left\{(x_1, x_2, \ldots, x_n): x_i \in D \text{ for each } i \right\} \] If the sampling is without replacement , the sample size \(n\) can be no larger than the population size \(m\). In this case, the sample space \(S\) consists of all permutations of size \(n\) chosen from \(D\): \[ S = D_n = \left\{(x_1, x_2, \ldots, x_n): x_i \in D \text{ for each } i \text{ and } x_i \ne x_j \text{ for all } i \ne j\right\} \]
From the multiplication principle of combinatorics,
- \(\#(D^n) = m^n\)
- \(\#(D_n) = m^{(n)} = m (m - 1) \cdots (m - n + 1)\)
With either type of sampling, we assume that the samples are equally likely and thus that the outcome variable \(\bs{X}\) is uniformly distributed on the appropriate sample space \(S\); this is the meaning of the phrase random sample : \[ \P(\bs{X} \in A) = \frac{\#(A)}{\#(S)}, \quad A \subseteq S \]
The Exchangeable Property
Suppose again that we select \(n\) objects at random from the population \(D\), either with or without replacement and record the ordered sample \(\bs{X} = (X_1, X_2, \ldots, X_n)\)
Any permutation of \(\bs{X}\) has the same distribution as \(\bs{X}\) itself, namely the uniform distribution on the appropriate sample space \(S\):
- \(D^n\) if the sampling is with replacement.
- \(D_n\) if the sampling is without replacement.
A sequence of random variables with this property is said to be exchangeable. Although this property is very simple to understand, both intuitively and mathematically, it is nonetheless very important. We will use the exchangeable property often in this chapter.
More generally, any sequence of \(k\) of the \(n\) outcome variables is uniformly distributed on the appropriate sample space:
- \(D^k\) if the sampling is with replacement.
- \(D_k\) if the sampling is without replacement.
In particular, for either sampling method, \(X_i\) is uniformly distributed on \(D\) for each \(i \in \{1, 2, \ldots, n\}\).
If the sampling is with replacement then \(\bs{X} = (X_1, X_2, \ldots, X_n)\) is a sequence of independent random variables.
Thus, when the sampling is with replacement, the sample variables form a random sample from the uniform distribution, in statistical terminology.
If the sampling is without replacement, then the conditional distribution of a sequence of \(k\) of the outcome variables, given the values of a sequence of \(j\) other outcome variables, is the uniform distribution on the set of permutations of size \(k\) chosen from the population when the \(j\) known values are removed (of course, \(j + k \le n\)).
In particular, \(X_i\) and \(X_j\) are dependent for any distinct \(i\) and \(j\) when the sampling is without replacement.
The Unordered Sample
In many cases when the sampling is without replacement, the order in which the objects are chosen is not important; all that matters is the (unordered) set of objects: \[ \bs{W} = \{X_1, X_2, \ldots, X_n\} \] The random set \(\bs{W}\) takes values in the set of combinations of size \(n\) chosen from \(D\): \[ T = \left\{ \{x_1, x_2, \ldots, x_n\}: x_i \in D \text{ for each } i \text{ and } x_i \ne x_j \text{ for all } i \ne j \right\} \]
Recall that \(\#(T) = \binom{m}{n}\).
\(\bs{W}\) is uniformly distributed over \(T\): \[ \P(\bs{W} \in B) = \frac{\#(B)}{\#(T)} = \frac{\#(B)}{\binom{m}{n}}, \quad B \subseteq T \]
Proof
For any combination of size \(n\) from \(D\), there are \(n!\) permutations of size \(n\).
Suppose now that the sampling is with replacement, and we again denote the unordered outcome by \(\bs{W}\). In this case, \(\bs{W}\) takes values in the collection of multisets of size \(n\) from \(D\). (A multiset is like an ordinary set, except that repeated elements are allowed). \[ T = \left\{ \{x_1, x_2, \ldots, x_n\}: x_i \in D \text{ for each } i \right\} \]
Recall that \(\#(T) = \binom{m + n - 1}{n}\).
\(\bs{W}\) is not uniformly distributed on \(T\).
Summary of Sampling Formulas
The following table summarizes the formulas for the number of samples of size \(n\) chosen from a population of \(m\) elements, based on the criteria of order and replacement.
| Number of samples | With order | Without |
|---|---|---|
| With replacement | \(m^n\) | \(\binom{m + n - 1}{n}\) |
| Without | \(m^{(n)}\) | \(\binom{m}{n}\) |
Examples and Applications
Suppose that a sample of size 2 is chosen from the population \(\{1, 2, 3, 4\}\). Explicitly list all samples in the following cases:
- Ordered samples, with replacement.
- Ordered samples, without replacement.
- Unordered samples, with replacement.
- Unordered samples, without replacement.
Answer
- \(\{(1,1), (1,2), (1,3), (1,4), (2,1), (2,2), (2,3), (2,4), (3,1), (3,2), (3,3), (3,4), (4,1), (4,2), (4,3), (4,4)\}\)
- \(\{(1,2), (1,3), (1,4), (2,1), (2,3), (2,4), (3,1), (3,2), (3,4), (4,1), (4,2), (4,3)\}\)
- \(\{\{1,1\}, \{1,2\}, \{1,3\}, \{1,4\}, \{2,2\}, \{2,3\}, \{2,4\}, \{3,3\}, \{3,4\}, \{4,4\}\}\)
- \(\{\{1,2\}, \{1,3\}, \{1,4\}, \{2,3\}, \{2,4\}, \{3,4\}\}\)
Multi-type Populations
A dichotomous population consists of two types of objects.
Suppose that a batch of 100 components includes 10 that are defective. A random sample of 5 components is selected without replacement. Compute the probability that the sample contains at least one defective component.
Answer
0.4162
An urn contains 50 balls, 30 red and 20 green. A sample of 15 balls is chosen at random. Find the probability that the sample contains 10 red balls in each of the following cases:
- The sampling is without replacement
- The sampling is with replacement
Answer
- 0.2070
- 0.1859
In the ball and urn experiment select 50 balls with 30 red balls, and sample size 15. Run the experiment 100 times. Compute the relative frequency of the event that the sample has 10 red balls in each of the following cases, and compare with the respective probability in the previous exercise:
- The sampling is without replacement
- The sampling is with replacement
Suppose that a club has 100 members, 40 men and 60 women. A committee of 10 members is selected at random (and without replacement, of course).
- Find the probability that both genders are represented on the committee.
- If you observed the experiment and in fact the committee members are all of the same gender, would you believe that the sampling was random?
Answer
- 0.9956
- No
Suppose that a small pond contains 500 fish, 50 of them tagged. A fisherman catches 10 fish. Find the probability that the catch contains at least 2 tagged fish.
Answer
0.2635
The basic distribution that arises from sampling without replacement from a dichotomous population is studied in the section on the hypergeometric distribution. More generally, a multi-type population consists of objects of \(k\) different types.
Suppose that a legislative body consists of 60 republicans, 40 democrats, and 20 independents. A committee of 10 members is chosen at random. Find the probability that at least one party is not represented on the committee.
Answer
0.1633. Use the inclusion-exclusion law.
The basic distribution that arises from sampling without replacement from a multi-type population is studied in the section on the multivariate hypergeometric distribution.
Cards
Recall that a standard card deck can be modeled by the product set \[ D = \{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, \jack, \queen, \king\} \times \{\clubsuit, \diamondsuit, \heartsuit, \spadesuit\} \] where the first coordinate encodes the denomination or kind (ace, 2-10, jack, queen, king) and where the second coordinate encodes the suit (clubs, diamonds, hearts, spades). The general card experiment consists of drawing \(n\) cards at random and without replacement from the deck \(D\). Thus, the \(i\)th card is \(X_i = (Y_i, Z_i)\) where \(Y_i\) is the denomination and \(Z_i\) is the suit. The special case \(n = 5\) is the poker experiment and the special case \(n = 13\) is the bridge experiment . Note that with respect to the denominations or with respect to the suits, a deck of cards is a multi-type population as discussed above.
In the card experiment with \(n = 5\) cards (poker), there are
- 311,875,200 ordered hands
- 2,598,960 unordered hands
In the card experiment with \(n = 13\) cards (bridge), there are
- 3,954,242,643,911,239,680,000 ordered hands
- 635,013,559,600 unordered hands
In the card experiment, set \(n = 5\). Run the simulation 5 times and on each run, list all of the (ordered) sequences of cards that would give the same unordered hand as the one you observed.
In the card experiment,
- \(Y_i\) is uniformly distributed on \(\{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, \jack, \queen, \king\}\) for each \(i\).
- \(Z_j\) is uniformly distributed on \(\{\clubsuit, \diamondsuit, \heartsuit, \spadesuit\}\) for each \(i\).
In the card experiment, \(Y_i\) and \(Z_j\) are independent for any \(i\) and \(j\).
In the card experiment, \((Y_1, Y_2)\) and \((Z_1, Z_2)\) are dependent.
Suppose that a sequence of 5 cards is dealt. Find each of the following:
- The probability that the third card is a spade.
- The probability that the second and fourth cards are queens.
- The conditional probability that the second card is a heart given that the fifth card is a heart.
- The probability that the third card is a queen and the fourth card is a heart.
Answer
- \(\frac{1}{4}\)
- \(\frac{1}{221}\)
- \(\frac{4}{17}\)
- \(\frac{1}{52}\)
Run the card experiment 500 time. Compute the relative frequency corresponding to each probability in the previous exercise.
Find the probability that a bridge hand will contain no honor cards that is, no cards of denomination 10, jack, queen, king, or ace. Such a hand is called a Yarborough , in honor of the second Earl of Yarborough.
Answer
0.000547
Dice
Rolling \(n\) fair, six-sided dice is equivalent to choosing a random sample of size \(n\) with replacement from the population \(\{1, 2, 3, 4, 5, 6\}\). Generally, selecting a random sample of size \(n\) with replacement from \(D = \{1, 2, \ldots, m\}\) is equivalent to rolling \(n\) fair, \(m\)-sided dice.
In the game of poker dice , 5 standard, fair dice are thrown. Find each of the following:
- The probability that all dice show the same score.
- The probability that the scores are distinct.
- The probability that 1 occurs twice and 6 occurs 3 times.
Answer
- \(\frac{1}{1296}\)
- \(\frac{5}{24}\)
- \(\frac{5}{3888}\)
Run the poker dice experiment 500 times. Compute the relative frequency of each event in the previous exercise and compare with the corresponding probability.
The game of poker dice is treated in more detail in the chapter on Games of Chance.
Birthdays
Supposes that we select \(n\) persons at random and record their birthdays . If we assume that birthdays are uniformly distributed throughout the year, and if we ignore leap years, then this experiment is equivalent to selecting a sample of size \(n\) with replacement from \(D = \{1, 2, \ldots, 365\}\). Similarly, we could record birth months or birth weeks.
Suppose that a probability class has 30 students. Find each of the following:
- The probability that the birthdays are distinct.
- The probability that there is at least one duplicate birthday.
Answer
- 0.2937
- 0.7063
In the birthday experiment, set \(m = 365\) and \(n = 30\). Run the experiment 1000 times and compare the relative frequency of each event in the previous exercise to the corresponding probability.
The birthday problem is treated in more detail later in this chapter.
Balls into Cells
Suppose that we distribute \(n\) distinct balls into \(m\) distinct cells at random. This experiment also fits the basic model, where \(D\) is the population of cells and \(X_i\) is the cell containing the \(i\)th ball. Sampling with replacement means that a cell may contain more than one ball; sampling without replacement means that a cell may contain at most one ball.
 Find each of the following:
- The probability that the balls are all in different cells.

Answer
- \(\frac{189}{625}\)
- \(\frac{1}{10000}\)
Coupons
Suppose that when we purchase a certain product (bubble gum, or cereal for example), we receive a coupon (a baseball card or small toy, for example), which is equally likely to be any one of \(m\) types. We can think of this experiment as sampling with replacement from the population of coupon types; \(X_i\) is the coupon that we receive on the \(i\)th purchase.
Suppose that a kid's meal at a fast food restaurant comes with a toy. The toy is equally likely to be any of 5 types. Suppose that a mom buys a kid's meal for each of her 3 kids. Find each of the following:
- The probability that the toys are all the same.
- The probability that the toys are all different.
Answer
- \(\frac{1}{25}\)
- \(\frac{12}{25}\)
The coupon collector problem is studied in more detail later in this chapter.
The Key Problem
Suppose that a person has \(n\) keys, only one of which opens a certain door. The person tries the keys at random. We will let \(N\) denote the trial number when the person finds the correct key.
Suppose that unsuccessful keys are discarded (the rational thing to do, of course). Then \(N\) has the uniform distribution on \(\{1, 2, \ldots, n\}\).
- \(\P(N = i) = \frac{1}{n}, \quad i \in \{1, 2, \ldots, n\}\).
- \(\E(N) = \frac{n + 1}{2}\).
- \(\var(N) = \frac{n^2 - 1}{12}\).
Suppose that unsuccessful keys are not discarded (perhaps the person has had a bit too much to drink). Then \(N\) has a geometric distribution on \(\N_+\).
- \(\P(N = i) = \frac{1}{n} \left( \frac{n-1}{n} \right)^{i-1}, \quad i \in \N_+\).
- \(\E(N) = n\).
- \(\var(N) = n (n - 1)\).
Simulating a Random Samples
It's very easy to simulate a random sample of size \(n\), with replacement from \(D = \{1, 2, \ldots, m\}\). Recall that the ceiling function \(\lceil x \rceil\) gives the smallest integer that is at least as large as \(x\).
Let \(\bs{U} = (U_1, U_2, \ldots, U_n)\) be a sequence of be a random numbers. Recall that these are independent random variables, each uniformly distributed on the interval \([0, 1]\) (the standard uniform distribution). Then \(X_i = \lceil m \, U_i \rceil\) for \(i \in \{1, 2, \ldots, n\}\) simulates a random sample, with replacement, from \(D\).
It's a bit harder to simulate a random sample of size \(n\), without replacement, since we need to remove each sample value before the next draw.
The following algorithm generates a random sample of size \(n\), without replacement, from \(D\).
- For \(i = 1\) to \(m\), let \(b_i = i\).
-
For \(i = 1\) to \(n\),
- let \(j = m - i + 1\)
- let \(U_i\) be a random number
- let \(J = \lfloor j U_i \rfloor\)
- let \(X_i = b_J\)
- let \(k = b_j\)
- let \(b_j = b_J\)
- let \(b_J = k\)
- Return \(\bs{X} = (X_1, X_2, \ldots, X_n)\)


18.4: Administering Intradermal Medications
Intradermal injections (ID) are administered into the dermis just below the epidermis. See Figure \(\PageIndex{1}\) [1] for an image of the layers of the skin. Intradermal (ID) injections have the longest absorption time of all parenteral routes because there are fewer blood vessels and no muscle tissue. These types of injections are used for sensitivity testing because the patient’s reaction is easy to visualize and the degree of reaction can be assessed. Examples of intradermal injections include tuberculosis (TB) and allergy testing. [2]
Anatomic Sites
The most common anatomical sites used for intradermal injections are the inner surface of the forearm and the upper back below the scapula. The nurse should select an injection site that is free from lesions, rashes, moles, or scars that may alter the visual inspection of the test results. See Figure \(\PageIndex{2}\) [3] for an image of the nurse inspecting a patient’s forearm site prior to injection.
Description of Procedure
Clean the site with an alcohol swab or antiseptic swab for 30 seconds using a firm, circular motion. Allow the site to dry. Allowing the skin to dry prevents introducing alcohol into the tissue, which can be irritating and uncomfortable. [4]
Use a tuberculin syringe, calibrated in tenths and hundredths of a milliliter, with a needle length of 1/4 inches to 1/2 inches and a gauge of 26 or 27. [5] See Figure \(\PageIndex{3}\) [6] for an image of a tuberculin syringe. Remove the cap from the needle by pulling it off in a straight motion. A straight motion helps prevent needlestick injury.
The dosage of an intradermal injection is usually under 0.5 mL, and the angle of administration for an ID injection is 5 to 15 degrees. Using your nondominant hand, spread the skin taut over the injection site. Taut skin provides easy entrance for the needle and is also important to do for older adults, whose skin is less elastic. See Figure \(\PageIndex{4}\) [7] of an image of a nurse holding the skin taut prior to injection. [8]
Hold the syringe in the dominant hand between the thumb and forefinger, with the bevel of the needle up at a 5- to 15-degree angle at the selected site. Place the needle almost flat against the patient’s skin, bevel side up, and insert the needle into the skin. Keeping the bevel side up allows for smooth piercing of the skin and induction of the medication into the dermis. Advance the needle no more than an eighth of an inch to cover the bevel. Once the syringe is in place, use the thumb of the nondominant hand to push on the plunger to slowly inject the medication. [9] See Figure \(\PageIndex{5}\) [10] for an image of a nurse administering an intradermal injection.
After the ID injection is completed, a bleb (small blister) should appear under the skin. The presence of the bleb indicates that the medication has been correctly placed in the dermis. See Figure \(\PageIndex{6}\) [11] for an image of a bleb.
Carefully withdraw the needle out of the insertion site using the same angle it was placed so as not to disturb the bleb. Withdrawing at the same angle as insertion also minimizes discomfort to the patient and damage to the tissue. Do not massage or cover the site. Massaging the area may spread the solution to the underlying subcutaneous tissue. Discard the syringe in the sharps container. If administering a TB test, advise the patient to return for a reading in 48-72 hours. Discard used supplies, remove gloves, perform hand hygiene, and document. [12]
- “ 501 Structure of the skin.jpg ” by OpenStax is licensed under CC BY 3.0 . Access for free at https://openstax.org/books/anatomy-and-physiology/pages/5-1-layers-of-the-skin . ↵
- This work is a derivative of Clinical Procedures for Safer Patient Care by British Columbia Institute of Technology and is licensed under CC BY 4.0↵
- “Inspecting Forearm” by Meredith Pomietlo for Chippewa Valley Technical College is licensed under CC BY 4.0 ↵
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7.2: Energy in chemical reactions
19
Harper College Chemistry Department
Chemical changes and their accompanying changes in energy are important parts of our everyday world ( Figure 1 ). The macronutrients in food (proteins, fats, and carbohydrates) undergo metabolic reactions that provide the energy to keep our bodies functioning. We burn a variety of fuels (gasoline, natural gas, coal) to produce energy for transportation, heating and the generation of electricity. Industrial chemical reactions use enormous amounts of energy to produce raw materials (such as iron and aluminum). Energy is then used to manufacture those raw materials into useful products, such as cars, skyscrapers, and bridges.
This chapter will introduce the basic ideas of an important area of science concerned with the amount of heat absorbed or released during chemical and physical changes—an area called thermochemistry. The concepts introduced in this chapter are widely used in almost all scientific and technical fields. Food scientists use them to determine the energy content of foods. Biologists study the energetics of living organisms, such as the metabolic combustion of sugar into carbon dioxide and water. The oil, gas, and transportation industries, renewable energy providers, and many others endeavor to find better methods to produce energy for our commercial and personal needs. Engineers strive to improve energy efficiency, find better ways to heat and cool our homes, refrigerate our food and drinks, and meet the energy and cooling needs of computers and electronics, among other applications. Understanding thermochemical principles is essential for chemists, physicists, biologists, geologists, every type of engineer, and just about anyone who studies or does any kind of science.
Energy
Energy can be defined as the capacity to supply heat or do work. One type of work ( w ) is the process of causing matter to move against an opposing force. For example, we do work when we inflate a bicycle tire—we move matter (the air in the pump) against the opposing force of the air already in the tire.
Like matter, energy comes in different types. One scheme classifies energy into two types: potential energy, the energy an object has because of its relative position, composition or condition and kinetic energy, the energy that an object possesses because of its motion. Water at the top of a waterfall or dam has potential energy because of its position; when it flows downward through generators, it has kinetic energy that can be used to do work and produce electricity in a hydroelectric plant ( Figure 2 ). A battery has potential energy because the chemicals within it can produce electricity that can do work.
Energy can be converted from one form into another, but all of the energy present before a change occurs always exists in some form after the change is completed. This observation is expressed in the law of conservation of energy: during a chemical or physical change, energy can be neither created nor destroyed, although it can be changed in form. (This is also one version of the first law of thermodynamics, as you will learn later.)
When one substance is converted into another, there is always an associated conversion of one form of energy into another. Heat is usually released or absorbed, but sometimes the conversion involves light, electrical energy or some other form of energy. For example, chemical energy (a type of potential energy) is stored in the molecules that compose gasoline. When gasoline is combusted within the cylinders of a car’s engine, the rapidly expanding gaseous products of this chemical reaction generate mechanical energy (a type of kinetic energy) when they move the cylinders’ pistons.
According to the law of conservation of matter (seen in an earlier chapter), there is no detectable change in the total amount of matter during a chemical change. When chemical reactions occur, the energy changes are relatively modest and the mass changes are too small to measure, so the laws of conservation of matter and energy hold well. However, in nuclear reactions, the energy changes are much larger (by factors of a million or so), the mass changes are measurable, and matter-energy conversions are significant. This will be examined in more detail in a later chapter on nuclear chemistry. To encompass both chemical and nuclear changes, we combine these laws into one statement: The total quantity of matter and energy in the universe is fixed.
Thermal Energy, Temperature and Heat
Thermal energy is kinetic energy associated with the random motion of atoms and molecules. Temperature is a quantitative measure of “hot” or “cold.” When the atoms and molecules in an object are moving or vibrating quickly, they have a higher average kinetic energy (KE) and we say that the object is “hot.” When the atoms and molecules are moving slowly, they have lower average KE and we say that the object is “cold” ( Figure 3 ). Assuming that no chemical reaction or phase change (such as melting or vaporizing) occurs, increasing the amount of thermal energy in a sample of matter will cause its temperature to increase. In addition, assuming that no chemical reaction or phase change (such as condensation or freezing) occurs, decreasing the amount of thermal energy in a sample of matter will cause its temperature to decrease.
Click on this interactive simulation to view the effects of temperature on molecular motion.
Most substances expand as their temperature increases and contract as their temperature decreases. This property can be used to measure temperature changes, as shown in Figure 4 . The operation of many thermometers depends on the expansion and contraction of substances in response to temperature changes.
The following demonstration allows one to view the effects of heating and cooling a coiled bimetallic strip.
Heat ( q ) is the transfer of thermal energy between two bodies at different temperatures. Heat flow (a redundant term, but one commonly used) increases the thermal energy of one body and decreases the thermal energy of the other. Suppose we initially have a high temperature (and high thermal energy) substance (H) and a low temperature (and low thermal energy) substance (L). The atoms and molecules in H have a higher average KE than those in L. If we place substance H in contact with substance L, the thermal energy will flow spontaneously from substance H to substance L. The temperature of substance H will decrease, as will the average KE of its molecules; the temperature of substance L will increase, along with the average KE of its molecules. Heat flow will continue until the two substances are at the same temperature ( Figure 5 ).
Matter undergoing chemical reactions and physical changes can release or absorb heat. A change that releases heat is called an exothermic process. For example, the combustion reaction that occurs when using an oxyacetylene torch is an exothermic process—this process also releases energy in the form of light as evidenced by the torch’s flame ( Figure 6 ). A reaction or change that absorbs heat is an endothermic process. A cold pack used to treat muscle strains provides an example of an endothermic process. When the substances in the cold pack (water and a salt like ammonium nitrate) are brought together, the resulting process absorbs heat, leading to the sensation of cold.
Historically, energy was measured in units of calories (cal). A calorie is the amount of energy required to raise one gram of water by 1 degree C (1 kelvin). However, this quantity depends on the atmospheric pressure and the starting temperature of the water. The ease of measurement of energy changes in calories has meant that the calorie is still frequently used. The Calorie (with a capital C), or large calorie, commonly used in quantifying food energy content, is a kilocalorie. The SI unit of heat, work and energy is the joule. A joule (J) is defined as the amount of energy used when a force of 1 newton moves an object 1 meter. It is named in honor of the English physicist James Prescott Joule. One joule is equivalent to 1 kg m 2 /s 2 , which is also called 1 newton–meter. A kilojoule (kJ) is 1000 joules. To standardize its definition, 1 calorie has been set to equal 4.184 joules.
Chemists are concerned with both physical and chemical change, and the energy associated with each. Chemical reactions involve the making and breaking of covalent bonds and these transformations have energy consequences. Heat is the most common form of energy introduced into or released from chemical reactions, but light, electrical current and sound may also be involved. Also, if gases are produced in a reaction, the work done on the surroundings by volume expansion becomes part of the energy balance, and in explosive reactions may be the major consequence. Of course, reactions that consume a gas undergo an opposite volume change and work is done on the system by the surroundings.
The covalent bond of a chlorine molecule provides a simple example of the energy changes associated with bond breaking and bond making. This bond may be broken by the introduction of heat or light energy and it has been determined that 57.9 kcal/mol (242.3 kJ/mol) is required to do so . This is shown in the first of the following reactions; the second reaction describes the reverse bond-forming process. The energy absorbed or released in these reactions is referred to as the bond dissociation energy . If the bond dissociation energy is introduced from the surroundings in the form of heat, the transformation is said to be endothermic . If heat passes from the system to the surroundings, the transformation is termed exothermic . Using our initial terminology, we may say that the covalently bonded system has a lower potential energy than the unbonded diatomic system. Indeed, it is helpful to think of exothermic reactions as proceeding from a higher energy (less stable) reactant state to a lower energy (more stable) product state, as shown in the diagram on the right. Some basic principles of reaction energetics were discussed earlier .
| Cl _ Cl + heat ____ > 2Cl • | An Endothermic Transformation | |
|---|---|---|
| 2Cl • ____ > Cl _ Cl + heat | An Exothermic Transformation |
In more complex chemical reactions some (or even all) of the bonds that hold together the atoms of reactant and product molecules may be broken while other bonds are formed. Energy is required to break bonds and since different bonds have different bond dissociation energies, there is often a significant overall energy change in the course of a reaction. In the combustion of methane, for example, all six bonds in the reactant molecules are broken and six new bonds are formed in the product molecules (equation 1). To analyze such reactions we need to keep track of and evaluate heat changes in a precise and systematic manner.
| (1) CH 4 + 2 O 2 | CO 2 + 2 H 2 O + heat | |
| Reactants | Products |
Glossary
bond dissociation energy
The energy absorbed or released in these reactions
- exothermic process
- A change that releases heat
- endothermic process
- A change that absorbs heat
- kinetic energy
- the energy that an object possesses because of its motion
-
- potential energy
- the energy an object has because of its relative position, composition or condition


5.14D: Biosynthesis of Tetrapyrroles
- Recall the process of tetrapyrrole biosynthesis
Porphyrins are a group of organic compounds, many naturally occurring. One of the best-known porphyrins is heme, the pigment in red blood cells. Heme is a cofactor of the protein hemoglobin. The main “application” of porphyrins is their role in supporting aerobic life. For example, complexes of meso-tetraphenylporphyrin, e.g., the iron(III) chloride complex (TPPFeCl), catalyze a variety of reactions of potential interest in organic synthesis.
Porphyrins are heterocyclic macrocycles composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (=CH-). Porphyrins are aromatic, obeying Hückel’s rule for aromaticity, possessing 4n+2 π electrons (n=4 for the shortest cyclic path) delocalized over the macrocycle. Thus, porphyrin macrocycles are highly conjugated systems. As a consequence, they typically have very intense absorption bands in the visible region and may be deeply colored. (The name porphyrin comes from a Greek word for purple. ) The macrocycle has 26 pi electrons in total. The parent porphyrin is porphine, and substituted porphines are called porphyrins.
Porphyrins are the conjugate acids of ligands that bind metals to form complexes. The metal ion usually has a charge of 2+ or 3+. A schematic equation for these syntheses is:
H 2 porphyrin + [MLn]2+ → M(porphyrinate)Ln-4 + 4 L + 2 H+
where M=metal ion and L=a ligand
A porphyrin without a metal ion in its cavity is a free base. Some iron-containing porphyrins are called hemes. Heme-containing proteins, or hemoproteins, are found extensively in nature. Hemoglobin and myoglobin are two O2-binding proteins that contain iron porphyrins. Various cytochromes are also hemoproteins. Several other heterocycles are related to porphyrins. These include corrins, chlorins, bacteriochlorophylls and corphins. Chlorins (2,3-dihydroporphyrin) are more reduced, contain more hydrogen than porphyrins, and feature a pyrroline subunit. This structure occurs in a chlorophyll molecule. Replacement of two of the four pyrrolic subunits with pyrrolinic subunits results in either a bacteriochlorin (as found in some photosynthetic bacteria) or an isobacteriochlorin, depending on the relative positions of the reduced rings. Some porphyrin derivatives follow Hückel’s rule, but most do not.
The “committed step” for porphyrin biosynthesis is the formation of δ-aminolevulinic acid (δ-ALA, 5-ALA or dALA) by the reaction of the amino acid glycine with succinyl-CoA from the citric acid cycle. Two molecules of dALA combine to give porphobilinogen (PBG), which contains a pyrrole ring. Four PBGs are then combined through deamination into hydroxymethyl bilane (HMB), which is hydrolysed to form the circular tetrapyrrole uroporphyrinogen III. This molecule undergoes a number of further modifications. Intermediates are used in different species to form particular substances, but, in humans, the main end-product protoporphyrin IX is combined with iron to form heme. Bile pigments are the breakdown products of heme.
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Key Points
- Porphyrins are a group of organic compounds, many naturally occurring, such as heme.
- Porphyrins are aromatic, obeying Hückel’s rule for aromaticity, possessing 4n+2 π electrons (n=4 for the shortest cyclic path) delocalized over the macrocycle.
- Porphyrin macrocycles are highly conjugated systems and typically have very intense absorption bands in the visible region, and may be deeply colored.
Key Terms
- heterocyclic : Having one or more atoms other than carbon in at least one of its rings.
- porphyrin : Any of a class of heterocyclic compounds containing four pyrrole rings arranged in a square; they are important in biochemistry in a form with a metal atom in the central cavity (hemoglobin with iron, chlorophyll with magnesium, etc.).
- aromatic : Having a closed ring of alternate single and double bonds with delocalized electrons.


6.1: Kinds of Organic Reactions
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Objective
After completing this section, you should be able to list and describe the four important “kinds” of reactions that occur in organic chemistry.
Key Terms
Make certain that you can define, and use in context, the key terms below.
- addition reaction
- elimination reaction
- rearrangement reaction
- substitution reaction
Study Notes
It is sufficient that you know the general form of each kind of reaction. However, given a chemical equation, you should be able to recognize which kind of reaction it involves.
If you scan any organic textbook you will encounter what appears to be a very large, often intimidating, number of reactions. These are the "tools" of a chemist, and to use these tools effectively, we must organize them in a sensible manner and look for patterns of reactivity that permit us make plausible predictions. Most of these reactions occur at special sites of reactivity known as functional groups, and these constitute one organizational scheme that helps us catalog and remember reactions.
Ultimately, the best way to achieve proficiency in organic chemistry is to understand how reactions take place, and to recognize the various factors that influence their course.
First, we identify four broad classes of reactions based solely on the structural change occurring in the reactant molecules. This classification does not require knowledge or speculation concerning reaction paths or mechanisms. The four main reaction classes are additions, eliminations, substitutions, and rearrangements.
Addition Reaction
Elimination Reaction
Substitution Reaction
Rearrangement Reaction
In an addition reaction the number of σ-bonds in the substrate molecule increases, usually at the expense of one or more π-bonds. The reverse is true of elimination reactions, i.e. the number of σ-bonds in the substrate decreases, and new π-bonds are often formed. Substitution reactions, as the name implies, are characterized by replacement of an atom or group (Y) by another atom or group (Z). Aside from these groups, the number of bonds does not change. A rearrangement reaction generates an isomer, and again the number of bonds normally does not change.
The examples illustrated above involve simple alkyl and alkene systems, but these reaction types are general for most functional groups, including those incorporating carbon-oxygen double bonds and carbon-nitrogen double and triple bonds. Some common reactions may actually be a combination of reaction types.
Example \(\PageIndex{1}\): Reaction of an Ester with Ammonia
The reaction of an ester with ammonia to give an amide, as shown below, appears to be a substitution reaction ( Y = CH 3 O & Z = NH 2 ); however, it is actually two reactions, an addition followed by an elimination.
Example \(\PageIndex{2}\): The Addition of water to a Nitrile
The addition of water to a nitrile does not seem to fit any of the above reaction types, but it is simply a slow addition reaction followed by a rapid rearrangement, as shown in the following equation. Rapid rearrangements of this kind are called tautomerizations .
Exercise \(\PageIndex{3}\)
Classify each reaction as addition, elimination, substitution, or rearrangement.
- Answer
-
A = Substitution; B = Elimination ; C = Addition


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14.1: DNA structure
44
Harper College Chemistry Department
Adapted from OpenStax: https://openstax.org/books/microbiol...unction-of-dna
LEARNING OBJECTIVES
- Describe the biochemical structure of deoxyribonucleotides
- Identify the base pairs used in the synthesis of deoxyribonucleotides
- Explain why the double helix of DNA is described as antiparallel
In previous chapters, we discussed the three classes of macromolecules: proteins, lipids and carbohydrates. In this chapter, we will discuss the genetic role of a fourth class of molecules: nucleic acids. Like other macromolecules, nucleic acid s are composed of monomers, called nucleotide s, which are polymerized to form large strands. Each nucleic acid strand contains certain nucleotides that appear in a certain order within the strand, called its base sequence . The base sequence of deoxyribonucleic acid (DNA) is responsible for carrying and retaining the hereditary information in a cell. In this section, we will discuss the basic structure and function of DNA.
DNA Nucleotides
The building blocks of nucleic acids are nucleotides. Nucleotides that compose DNA are called deoxyribonucleotides . The three components of a deoxyribonucleotide are a five-carbon sugar called deoxyribose , a phosphate group, and a nitrogenous base , a nitrogen-containing ring structure that is responsible for complementary base pairing between nucleic acid strands ( Figure 1 ). The carbon atoms of the five-carbon deoxyribose are numbered 1ʹ, 2ʹ, 3ʹ, 4ʹ, and 5ʹ (1ʹ is read as “one prime”). A nucleoside comprises the five-carbon sugar and nitrogenous base.
The deoxyribonucleotide is named according to the nitrogenous bases ( Figure 2 ). The nitrogenous bases adenine (A) and guanine (G) are the purines ; they have a double-ring structure with a six-carbon ring fused to a five-carbon ring. The pyrimidines , cytosine (C) and thymine (T), are smaller nitrogenous bases that have only a six-carbon ring structure.
Individual nucleoside triphosphates combine with each other by covalent bonds known as 5ʹ-3ʹ phosphodiester bonds , or linkages whereby the phosphate group attached to the 5ʹ carbon of the sugar of one nucleotide bonds to the hydroxyl group of the 3ʹ carbon of the sugar of the next nucleotide. Phosphodiester bonding between nucleotides forms the sugar-phosphate backbone , the alternating sugar-phosphate structure composing the framework of a nucleic acid strand ( Figure 3 ). During the polymerization process, deoxynucleotide triphosphates (dNTP) are used. To construct the sugar-phosphate backbone, the two terminal phosphates are released from the dNTP as a pyrophosphate. The resulting strand of nucleic acid has a free phosphate group at the 5ʹ carbon end and a free hydroxyl group at the 3ʹ carbon end. The two unused phosphate groups from the nucleotide triphosphate are released as pyrophosphate during phosphodiester bond formation. Pyrophosphate is subsequently hydrolyzed, releasing the energy used to drive nucleotide polymerization.
CHECK YOUR UNDERSTANDING
- What is meant by the 5ʹ and 3ʹ ends of a nucleic acid strand?
Discovering the Double Helix
By the early 1950s, considerable evidence had accumulated indicating that DNA was the genetic material of cells and now the race was on to discover its three-dimensional structure. Around this time, Austrian biochemist Erwin Chargaff 5 (1905–2002) examined the content of DNA in different species and discovered that adenine, thymine, guanine, and cytosine were not found in equal quantities, and that it varied from species to species, but not between individuals of the same species. He found that the amount of adenine was very close to equaling the amount of thymine, and the amount of cytosine was very close to equaling the amount of guanine, or A = T and G = C. These relationships are also known as Chargaff’s rules .
Other scientists were also actively exploring this field during the mid-20th century. In 1952, American scientist Linus Pauling (1901–1994) was the world’s leading structural chemist and odds-on favorite to solve the structure of DNA. Pauling had earlier discovered the structure of protein α helices, using X-ray diffraction , and based upon X-ray diffraction images of DNA made in his laboratory, he proposed a triple-stranded model of DNA. 6 At the same time, British researchers Rosalind Franklin (1920–1958) and her graduate student R.G. Gosling were also using X-ray diffraction to understand the structure of DNA ( Figure 4 ). It was Franklin’s scientific expertise that resulted in the production of more well-defined X-ray diffraction images of DNA that would clearly show the overall double-helix structure of DNA.
James Watson (1928–), an American scientist, and Francis Crick (1916–2004), a British scientist, were working together in the 1950s to discover DNA’s structure. They used Chargaff’s rules and Franklin and Wilkins ’ X-ray diffraction images of DNA fibers to piece together the purine-pyrimidine pairing of the double helical DNA molecule ( Figure 5 ). In April 1953, Watson and Crick published their model of the DNA double helix in Nature . 7 The same issue additionally included papers by Wilkins and colleagues, 8 as well as by Franklin and Gosling , 9 each describing different aspects of the molecular structure of DNA. In 1962, James Watson, Francis Crick, and Maurice Wilkins were awarded the Nobel Prize in Physiology and Medicine. Unfortunately, by then Franklin had died, and Nobel prizes at the time were not awarded posthumously. Work continued, however, on learning about the structure of DNA. In 1973, Alexander Rich (1924–2015) and colleagues were able to analyze DNA crystals to confirm and further elucidate DNA structure. 10
CHECK YOUR UNDERSTANDING
- Which scientists are given most of the credit for describing the molecular structure of DNA?
DNA Structure
Watson and Crick proposed that DNA is made up of two strands that are twisted around each other to form a right-handed helix. The two DNA strands are antiparallel , such that the 3ʹ end of one strand faces the 5ʹ end of the other ( Figure 6 ). The 3ʹ end of each strand has a free hydroxyl group, while the 5ʹ end of each strand has a free phosphate group. The sugar and phosphate of the polymerized nucleotides form the backbone of the structure, whereas the nitrogenous bases are stacked inside. These nitrogenous bases on the interior of the molecule interact with each other, base pairing.
Analysis of the diffraction patterns of DNA has determined that there are approximately 10 bases per turn in DNA. The asymmetrical spacing of the sugar-phosphate backbones generates major grooves (where the backbone is far apart) and minor grooves (where the backbone is close together) ( Figure 6 ). These grooves are locations where proteins can bind to DNA. The binding of these proteins can alter the structure of DNA, regulate replication , or regulate transcription of DNA into RNA.
Base pairing takes place between a purine and pyrimidine. In DNA, adenine (A) and thymine (T) are complementary base pairs , and cytosine (C) and guanine (G) are also complementary base pairs, explaining Chargaff’s rules ( Figure 7 ). The base pairs are stabilized by hydrogen bonds; adenine and thymine form two hydrogen bonds between them, whereas cytosine and guanine form three hydrogen bonds between them.
In the laboratory, exposing the two DNA strands of the double helix to high temperatures or to certain chemicals can break the hydrogen bonds between complementary bases, thus separating the strands into two separate single strands of DNA (single-stranded DNA [ ssDNA ]). This process is called DNA denaturation and is analogous to protein denaturation, as described in Proteins . The ssDNA strands can also be put back together as double-stranded DNA ( dsDNA ), through reannealing or renaturing by cooling or removing the chemical denaturants, allowing these hydrogen bonds to reform. The ability to artificially manipulate DNA in this way is the basis for several important techniques in biotechnology ( Figure 8 ). Because of the additional hydrogen bonding between the C = G base pair, DNA with a high GC content is more difficult to denature than DNA with a lower GC content.
LINK TO LEARNING
View an animation on DNA structure from the DNA Learning Center to learn more.
CHECK YOUR UNDERSTANDING
- What are the two complementary base pairs of DNA and how are they bonded together?
DNA Function
DNA stores the information needed to build and control the cell. The transmission of this information from mother to daughter cells is called vertical gene transfer and it occurs through the process of DNA replication. DNA is replicated when a cell makes a duplicate copy of its DNA, then the cell divides, resulting in the correct distribution of one DNA copy to each resulting cell. DNA can also be enzymatically degraded and used as a source of nucleosides and nucleotides for the cell. Unlike other macromolecules, DNA does not serve a structural role in cells.
CHECK YOUR UNDERSTANDING
- How does DNA transmit genetic information to offspring?
EYE ON ETHICS
Paving the Way for Women in Science and Health Professions
Historically, women have been underrepresented in the sciences and in medicine, and often their pioneering contributions have gone relatively unnoticed. For example, although Rosalind Franklin performed the X-ray diffraction studies demonstrating the double helical structure of DNA, it is Watson and Crick who became famous for this discovery, building on her data. There still remains great controversy over whether their acquisition of her data was appropriate and whether personality conflicts and gender bias contributed to the delayed recognition of her significant contributions. Similarly, Barbara McClintock did pioneering work in maize (corn) genetics from the 1930s through 1950s, discovering transposons (jumping genes), but she was not recognized until much later, receiving a Nobel Prize in Physiology or Medicine in 1983 ( Figure 10.19 ).
Today, women still remain underrepresented in many fields of science and medicine. While more than half of the undergraduate degrees in science are awarded to women, only 46% of doctoral degrees in science are awarded to women. In academia, the number of women at each level of career advancement continues to decrease, with women holding less than one-third of the positions of Ph.D.-level scientists in tenure-track positions, and less than one-quarter of the full professorships at 4-year colleges and universities. 11 Even in the health professions, like nearly all other fields, women are often underrepresented in many medical careers and earn significantly less than their male counterparts, as shown in a 2013 study published by the Journal of the American Medical Association . 12
Why do such disparities continue to exist and how do we break these cycles? The situation is complex and likely results from the combination of various factors, including how society conditions the behaviors of girls from a young age and supports their interests, both professionally and personally. Some have suggested that women do not belong in the laboratory, including Nobel Prize winner Tim Hunt, whose 2015 public comments suggesting that women are too emotional for science 13 were met with widespread condemnation.
Perhaps girls should be supported more from a young age in the areas of science and math ( Figure 10.19 ). Science, technology, engineering, and mathematics (STEM) programs sponsored by the American Association of University Women (AAUW) 14 and National Aeronautics and Space Administration (NASA) 15 are excellent examples of programs that offer such support. Contributions by women in science should be made known more widely to the public, and marketing targeted to young girls should include more images of historically and professionally successful female scientists and medical professionals, encouraging all bright young minds, including girls and women, to pursue careers in science and medicine.
CLINICAL FOCUS
Part 2
Based upon his symptoms, Alex’s physician suspects that he is suffering from a foodborne illness that he acquired during his travels. Possibilities include bacterial infection (e.g., enterotoxigenic E. coli , Vibrio cholerae , Campylobacter jejuni , Salmonella ), viral infection (rotavirus or norovirus), or protozoan infection ( Giardia lamblia , Cryptosporidium parvum , or Entamoeba histolytica ).

Alex’s stool sample showed neither blood nor cysts. Following analysis of his stool sample and based upon his recent travel history, the hospital physician suspected that Alex was suffering from traveler’s diarrhea caused by enterotoxigenic E. coli ( ETEC ), the causative agent of most traveler’s diarrhea. To verify the diagnosis and rule out other possibilities, Alex’s physician ordered a diagnostic lab test of his stool sample to look for DNA sequences encoding specific virulence factors of ETEC. The physician instructed Alex to drink lots of fluids to replace what he was losing and discharged him from the hospital.
ETEC produces several plasmid-encoded virulence factors that make it pathogenic compared with typical E. coli . These include the secreted toxins heat-labile enterotoxin (LT) and heat-stabile enterotoxin (ST) , as well as colonization factor (CF) . Both LT and ST cause the excretion of chloride ions from intestinal cells to the intestinal lumen, causing a consequent loss of water from intestinal cells, resulting in diarrhea. CF encodes a bacterial protein that aids in allowing the bacterium to adhere to the lining of the small intestine.
- Why did Alex’s physician use genetic analysis instead of either isolation of bacteria from the stool sample or direct Gram stain of the stool sample alone?
Jump to the next Clinical Focus box. Go back to the previous Clinical Focus box.
Footnotes
- 5 N. Kresge et al. “Chargaff’s Rules: The Work of Erwin Chargaff.” Journal of Biological Chemistry 280 (2005):e21.
- 6 L. Pauling, “A Proposed Structure for the Nucleic Acids.” Proceedings of the National Academy of Science of the United States of America 39 no. 2 (1953):84–97.
- 7 J.D. Watson, F.H.C. Crick. “A Structure for Deoxyribose Nucleic Acid.” Nature 171 no. 4356 (1953):737–738.
- 8 M.H.F. Wilkins et al. “Molecular Structure of Deoxypentose Nucleic Acids.” Nature 171 no. 4356 (1953):738–740.
- 9 R. Franklin, R.G. Gosling. “Molecular Configuration in Sodium Thymonucleate.” Nature 171 no. 4356 (1953):740–741.
- 10 R.O. Day et al. “A Crystalline Fragment of the Double Helix: The Structure of the Dinucleoside Phosphate Guanylyl-3′,5′-Cytidine.” Proceedings of the National Academy of Sciences of the United States of America 70 no. 3 (1973):849–853.
- 11 N.H. Wolfinger “For Female Scientists, There’s No Good Time to Have Children.” The Atlantic July 29, 2013. http://www.theatlantic.com/sexes/arc...ildren/278165/ .
- 12 S.A. Seabury et al. “Trends in the Earnings of Male and Female Health Care Professionals in the United States, 1987 to 2010.” Journal of the American Medical Association Internal Medicine 173 no. 18 (2013):1748–1750.
- 13 E. Chung. “Tim Hunt, Sexism and Science: The Real ‘Trouble With Girls’ in Labs.” CBC News Technology and Science , June 12, 2015. http://www.cbc.ca/news/technology/ti...labs-1.3110133 . Accessed 8/4/2016.
- 14 American Association of University Women. “Building a STEM Pipeline for Girls and Women.” http://www.aauw.org/what-we-do/stem-education/ . Accessed June 10, 2016.
- 15 National Aeronautics and Space Administration. “Outreach Programs: Women and Girls Initiative.” http://women.nasa.gov/outreach-programs/ . Accessed June 10, 2016.


9.5: Acting as a Respectful Listener
The Golden Rule suggests that people treat others how they would expect others to treat them, and in public speaking, this rule holds especially true.
Note to Self
Home Electronic Distraction
During speeches, avoid phone, tablet, or laptop use, unless previously arranged with the speaker in advance due to a special and documented accommodation need. With electronic devices, it is almost impossible not to check email, the internet, or social media. Studies indicate that this kind of multitasking impairs learning ( Murphy Paul, 2013 ); once people engage with electronic devices, they no longer pay attention to what happens in the room.
Shouldn’t audience members have the choice about whether they want to use their time engaging actively with the material at hand, or whether they would prefer to multitask? After all, they think they are not bothering anyone as they quietly read email or check social media platforms. This assumption has flaws. First, such activity damages the learning environment for others, even when conducted in silence. A study (Sana, Weston, & Cepeda, 2013) found that, not only did the multitasking student in a classroom do worse on a post-class test on the material, so did the peers who could see the computer. In other words, the off-task laptop use distracted not only the laptop user, but also the group of students surrounding the laptop user.
In addition, the speaker can find multitasking on a laptop a bit distracting because sometimes the audience member does not type at the most opportune times. Typing suggests the “listener” has more important things to do than engaging with the topic and listening to the speaker. That thought alone serves to distract the speaker’s attention.
Also consider the speaking environment. When working on a laptop, the speaker’s attention gets drawn to the back of the computer screen, rather than sustaining eye contact with the user. Learning in communication happens best when everyone actively engages with one another in the exchange of information. This can mean looking up from taking notes to listen, which means making strategic decisions about what to write down. Note taking should support the learning and retention of material; note taking itself does not qualify as learning.
A 2014 study (Mueller & Oppenheimer, 2014) that got a lot of attention in mainstream press suggests that taking notes by hand rather than typing them on a laptop improves comprehension of the material. While students taking notes on a laptop (and only taking notes—they were not allowed to multitask) wrote down more of the material covered in class, they often typed what the instructor said verbatim, which seems to have led to them process the material less. Meanwhile, the students taking notes by hand had to synthesize and condense as they wrote because they could not get everything down. As a result, they learned and retained the material better. Handwritten pages also permit the opportunity to easily create visual connections through the use of arrows, flowcharts, etc.
In public speaking scenarios, it’s best to break addictive patterns with regard to email, texting, social media, and internet usage. It may seem a bit silly to find it difficult to go for an hour without checking a phone or other electronic devices, but it happens quite often. Modern life offers many distractions, and though checking devices may have become a force of habit, people can use the opportunity as a listener to create or reinforce a habit of not checking them as well.
Provide Encouragement
One of the best ways to support a speaker is to provide solid nonverbal encouragement while staying mindful of the nonverbal messages sent. First, start with eye contact. Full, consistent, and prolonged eye contact tells speakers they have garnered attention. Also, sit up straight or lean forward, as this posture also suggests a higher sense of immediacy or intention to become involved in the communication taking place. If the speaker mentions something agreeable, smile in approval and show support with a head nod, though do not make it appear fake or forced.
Speakers, like many other performers (singers, athletes, dancers, etc.) derive their energy from supportive crowds. When crowds lack energy, it tends to deflate the impact of the message. The more encouragement the audience provides to the speaker, the more confident the presenter becomes. In return, as the speaker’s performance improves with the audience’s encouragement, their return on investment grows larger as well, since they witness a much higher caliber of speech.


2.8: II Glossary
ABCs: Airway, breathing, and circulation.
Actual problems: Nursing problems currently occurring with the patient.
Acuity: The level of patient care that is required based on the severity of a patient’s illness or condition.
Acuity-rating staffing models: A staffing model used to make patient assignments that reflects the individualized nursing care required for different types of patients.
Acute conditions: Conditions having a sudden onset.
Chronic conditions: Conditions that have a slow onset and may gradually worsen over time.
Clinical reasoning: “A complex cognitive process that uses formal and informal thinking strategies to gather and analyze patient information, evaluate the significance of this information, and weigh alternative actions.” [1]
Critical thinking: A broad term used in nursing that includes “reasoning about clinical issues such as teamwork, collaboration, and streamlining workflow.” [2]
CURE hierarchy: A strategy for prioritization based on identifying “critical” needs, “urgent” needs, “routine” needs, and “extras.”
Data cues: Pieces of significant clinical information that direct the nurse toward a potential clinical concern or a change in condition.
Expected conditions: Conditions that are likely to occur or anticipated in the course of an illness, disease, or injury.
Maslow’s hierarchy of needs: Prioritization strategies often reflect the foundational elements of physiological needs and safety and progress toward higher levels.
Ratio-based staffing models: A staffing model used to make patient assignments in terms of one nurse caring for a set number of patients.
Risk problem: A nursing problem that reflects that a patient may experience a problem but does not currently have signs reflecting the problem is actively occurring.
Time estimation: A prioritization strategy including the review of planned tasks and allocation of time believed to be required to complete each task.
Time scarcity: A feeling of racing against a clock that is continually working against you.
Unexpected conditions: Conditions that are not likely to occur in the normal progression of an illness, disease, or injury.
- Klenke-Borgmann, L., Cantrell, M. A., & Mariani, B. (2020). Nurse educator’s guide to clinical judgment: A review of conceptualization, measurement, and development. Nursing Education Perspectives, 41( 4), 215-221. https://doi.org/10.1097/01.nep.0000000000000669 ↵
- Klenke-Borgmann, L., Cantrell, M. A., & Mariani, B. (2020). Nurse educator’s guide to clinical judgment: A review of conceptualization, measurement, and development. Nursing Education Perspectives, 41( 4), 215-221. https://doi.org/10.1097/01.nep.0000000000000669 ↵


1.8: Discussion
Over coffee after their first combinatorics class, Xing remarked “This doesn't seem to be going like calculus. I'm expecting the professor to teach us how to solve problems—at least some kinds of problems. Instead, a whole bunch of problems were posed and we were asked whether we could solve them.”
Yolanda jumped in, saying “You may be judging things too quickly. I'm fascinated by these kinds of questions. They're different.”
Zori grumpily laid bare her concerns: “After getting out of Georgia Tech, who's going to pay me to count necklaces, distribute library books or solve Sudoku puzzles?”
Bob politely countered, “But the problems on networks and graphs seemed to have practical applications. I heard my uncle, a very successful business guy, talk about franchising problems that sound just like those.”
Alice speculated, “All those network problems sound the same to me. A fair to middling computer science major could probably write programs to solve any of them.”
Dave mumbled, “Maybe not. Similar sounding problems might actually be quite different in the end. Maybe we'll learn to tell the difference.”
After a bit of quiet time interrupted only by lattes disappearing, Carlos said softly, “It might not be so easy to distinguish hard problems from easy ones.”
Alice followed, “Regardless, what strikes me is that we all, well almost all of us,” she said, rolling her eyes at Bob, “seem to understand everything talked about in class today. It was so very concrete. I liked that.”


2.1: Introduction
The patients and families who come from our communities represent unlimited diversity that can be both visible and invisible. But even seemingly visible factors like a person’s race and age may not be what they appear. Nurses must not make assumptions about their patients. Only by being culturally competent and systematically asking culturally sensitive questions are nurses able to provide the best care.
To be inclusive of all patients who require obstetric and gynecologic care, this textbook uses the terms person assigned female at birth (AFAB) and pregnant person as well as others. In addition to caring for people of all races, ages, abilities, ethnicities, and religions, nurses care for people of all gender identities and sexual orientations. All are members of the community served by nurses, and all deserve culturally competent nursing care.