Chapter 6, Problem 25P

Summary Introduction

To analyze:

A rII lysis mutation resulted from a point mutation is tested against numerous deletion mutations. A series of seven point mutations are mapped along the rIIA gene, and these are tested for their capability of producing wild-type recombinants when crossed with rII partial-deletion mutants. The results are listed in the table below, the “$+$”sign indicates the formation of wild-type recombinants and “$-$” indicates that wild-type recombinants are not formed.

Using this data, show the stretch and end-points of each deletions as precisely as you can.

Deletion Mutation	Point mutation
	12	19	21	27	34	37	46
B622	+	+	-	+	+	+	-
CT48	-	+	+	-	-	+	+
MB101	+	+	+	+	+	-	-
VG14	+	-	+	+	+	+	+
N220	+	-	-	+	-	+	+

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 by reversion. The deletion mutations are non-revertible mutations that lose the gene sequence, and the deleted sequence cannot be restored; hence, it cannot form wild-type recombinants.

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.