Question $1(9$ marks$)$ In a generalized$-$transduction experiment, phages are collected from an E$.$ coli

donor strain of genotype cys$+$ leu$+$ thr$+$ and used to transduce a recipient of genotype cys$-$ leu$-$ thr$-.$

Initially, the treated recipient population is plated on a minimal medium supplemented with leucine and

threonine. Many colonies are obtained.

$($a$)$ List all possible genotypes of these colonies with respect to the three genes. $(2$ marks$)$

$($b$)$ The colonies are then tested to see if they can grow on three different types of media:$(1)$ minimal plus

threonine only $(2)$ minimal plus leucine only, and $(3)$ minimal. For each of these media, what genotypes

could, in theory, grow on that media. $(3$ marks$)$

Media Genotype$($s$)$

$1$

$2$

$3$

$($c$)$ Of the original colonies, $56\%$ are observed to grow on medium $1,5\%$ on medium $2,$ and no colonies

on medium $3.$ What are the actual genotypes of the colonies that grew on media $1$ and $2.(2$ marks$)$

Media Genotype$($s$)$

$1$

$2$

$($d$)$ Draw a map showing the order of the three genes and that indicates which of the two outer genes is

closer to the middle gene. $(2$ marks$)$