A selection of Mechanical calculators: The basic operating principles of mechanical calculators changed little from the end of the 19th century to their obsolescence in the 1970s, though there were many developments in the mechanisms and the materials used.
Post. Share. Bacteriophages are viruses that infect bacteria. A bacteriophage can have a protein tail attached to the capsid (protein coat that envelopes the genetic material), which is used to infect the host bacteria.Scientists have long sought to uncover the structure and function of viruses. bacteriophage can have a protein tail attached to the capsid (protein coat that envelopes the genetic material), which is used to infect the host bacteria.
This association is called lysogeny, and the integrated phage DNA is referred to as a prophage (Figure 6-19). Under certain conditions, the prophage DNA is activated, leading to its excision from the host-cell chromosome and entrance into the lytic cycle. Bacterial viruses of this type are called temperate phages. virus is a small parasite that cannot reproduce by itself. Once it infects a susceptible cell, however, a virus can direct the cell machinery to produce more viruses. Most viruses have either RNA or DNA as their genetic material.