A plaque assay is performed beginning with 1 mL of a solution containing bacteriophages. This solution is serially diluted three times by combining 0.1 mL of each sequential dilution with 9.9 mL of liquid medium. Then 0.1 mL of the final dilution is plated in the plaque assay and yields 17 plaques. What is the initial density of bacteriophages in the original 1 mL?

In studies of recombination between mutants 1 and 2 from Problem 21, the results shown in the following table were obtained.

When mutant 6 was tested for recombination with mutant 1, the data were the same as those shown above for strain B, but not for K12. The researcher lost the K12 data but remembered that recombination was ten times more frequent than when mutants 1 and 2 were tested. What were the lost values (dilution and plaque numbers)?

In studies of recombination between mutants 1 and 2 from Problem 21, the results shown in the following table were obtained.

Calculate the recombination frequency.

Define the term genetic complementation.

Describe how the term applies to an experiment in which two lysis-defective bacteriophages are able to coinfect a bacterial cell and produce lysis.

A plaque assay studies viruses through what measurement?

A mixed infection of two bacteriophage strains is often used for what purpose?

A mixed infection of two bacteriophage strains was performed. Infection of bacteriophage strain 1 causes the bacteria to be red and large, while infection of bacteriophage strain 2 causes the bacteria colony to be black and small. The following results were obtained. Using this data, determine the distance between the color and size genes.

In this chapter, we have focused on genetic systems present in bacteria and on the viruses that use bacteria as hosts (bacteriophages). In particular, we discussed mechanisms by which bacteria and their phages undergo genetic recombination, which allows geneticists to map bacterial and bacteriophage chromosomes. In the process, we found many opportunities to consider how this information was acquired. From the explanations given in the chapter, what answers would you propose to the following questions? How do we know that in bacteriophage T4 the rII locus is subdivided into two regions, or cistrons?