An EColi F^- Strain Has the Following Genotype: S^-U^-R^-I^-E^-C^- The Positions of Hfr 2,the Gene C,and the Polarity of Hfr

question 7

Essay

An E.coli F^- strain has the following genotype: S^-U^-R^-I^-E^-C^-.Three different Hfr strains,all carrying S⁺U⁺R⁺I⁺E⁺ and C⁺ markers and all having lambda phages integrated at the same specific site in their chromosomes are mated with the F strain in separate matings.The interrupted-mating results are given below.The numbers indicate time (in minutes)when different donor markers appeared in F^- cells after conjugation began.Assume that the E.coli map consists of 100 minutes,and gene C is mapped at 80 minutes.
$\begin{array}{llll}\text { Marker'S } & \text { Hfr 1 } &\text { Hfr 2 } & \text { Hfr } 3\\\hline R & 10 & 20 & - \\I & 40 & - & 5 \\U & 25 & 5 & - \\E & - & 60 & - \\C & - & 45 & - \\S & 55 & - & 20\end{array}$

The positions of Hfr 2,the gene C,and the polarity of Hfr 2 are given in the accompanying map.
a)Give the gene order,starting from C and going clockwise.
b)What is the location of the origin of Hfr 1? Hfr 3?
c)What is the location of the I marker? The S marker?
d)What is the location of the lambda phage in these strains?

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