b. To determine the relative order of the trp, pyr, and cys markers and the dist

Question

b. To determine the relative order of the trp, pyr, and cys markers and the distances between them, HfrEB was mated with the F strain long enough to allow transfer of the nic marker, after which Trp recom binants were selected, The unselected markers pyr and cys were then scored in the Trp recombinants, vielding the following results: Number of recombinants 790 145 60 Trp Draw a map of the trp, pyr, and cys markers relative to each other. (Note that you cannot determine the order relative to the nic or his genes using these data.) Express map distances between adjacent genes as the frequency of crossing-over between them.

Explanation / Answer

The order of markers is Tyr--- Cys--- Pyr

Map distance = (Number of recombinants / Total number of offspring) * 100

Map distance = (60+5/1000) * 100 = 6.5 mapunit or cM

The genotypes of lowest frequency are recombinants

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