Chapter 7, Problem 19CONQ

Summary Introduction

To analyze:

The length of a regular gene in a bacteriophage is a few hundred or a few thousand nucleotides. If a rapid-lysis phenotype is observed in two different strains of bacteriophage $\text{T4}$ that have a mutation in rIIA gene and when they are coinfected into E. coli (Bacteria), they never produce normal phages by intragenic recombination.

From the above information, question asked to make conclusions on the locations of the mutations in two different $\text{T4}$ strains.

Introduction:

A complementation test is a cis-trans test used to determine whether the mutations in two strains are in the same genes or different genes. When a mutation occurs in the same gene, complementation will not occur whereas mutation in different genes would result in complementation in a wild type phenotype.

In the given experiment, phages with rII mutations are unable to form plaques in E. coli. This observation is important to know the type of mutation in strains (Is it present on the same gene).

When different strains have mutation on same gene, complementation does not occur, and strains are unable to form plaque, but sometimes, these strains of viruses are able to form plaque at low rate because of rare intragenic recombination; if intragenic recombination does not occur, this indicates that mutation is in the same gene and same locus.