Chapter 6, Problem 15P

Summary Introduction

To analyze:

An rII lysis mutation resulting from a point mutation is tested against numerous deletion mutations shown in the figure below that are able to form wild-type recombinants.

These deletion mutants are categorized in two groups named- series I and II.

The results are listed in the table below, “$+$”sign indicates the formation of wild-type recombinants and “$-$” indicates that wild-type recombinants are not formed.

Determine the segment of rII region that has lysis mutant by using the entire data of Series I.

Use the Series II data to locate the exact point mutation. Explain the justifications for the identified mutation location for both the data of series I and II.

Series I		Series II
Deletion Mutation	Result	Deletion Mutation	Result
$\text{1272}$	$\text{-}$	$\text{1364}$	$\text{+}$
$\text{1241}$	$\text{-}$	$\text{EM66}$	$\text{-}$
$\text{J3}$	$\text{-}$	$\text{386}$	$\text{+}$
$\text{PT1}$	$\text{+}$	$\text{168}$	$\text{+}$
$\text{PB242}$	$\text{+}$	$\text{1993}$	$\text{-}$
$\text{A105}$	$\text{+}$	$\text{1695}$	$\text{-}$
$\text{638}$	$\text{+}$	$\text{PT153}$	$\text{+}$
		$\text{1231}$	$\text{-}$
		$\text{C33}$	$\text{+}$
		$\text{250}$	$\text{-}$

Introduction:

The recombination frequency expresses the distance among genes. Least the recombination frequency, closer the genes are while greater recombination frequencies show that the gene distance is more.

Point mutation is either deletion or addition of a nucleotide in a sequence of gene, which has the ability to return in their wild type phenotype.

The deletion mutant line of $\text{T4}$ phages generated are unable to return in their wild type phenotype.

There are two types of mutants in $\text{T4}$ phages i.e. revertible and non-revertible mutants. If these mutants are crossed, these will either form wild-type recombinants or not.