Question

You are checking the sequence of 3 genes using generalized transduction mapping. The recipient is Leu-,  Azi^S, Thr- while the donor is Leu+,  Azi^R, Thr +. If you select the Leu+ as marker,  Azi^R would be 50% while Thr+ would be 2%. If you select Thr+ as marker Leu+ would be 3% and Azi^R would be 0%. What is the sequence?

(a) Thr Leu Azi

(b) Azi Thr Leu

(c) Azi Leu Thr

(d) Thr Azi Leu

This question was addressed to me in an online interview.

My enquiry is from Gene Mapping in Bacteria by Transduction in division Genomics : The Mapping and Sequencing of Genomes of Cytogenetics

Answer 1

Right answer is (a) Thr Leu Azi

Easiest explanation: Genes Leu and Azi and genes Leu and Thr have a tendency to be incorporated together; this is as a result of their physical proximity. On the other hand Thr and azi hardy show such tendency so they must be farther apart. This results in the sequence with Leu in the middle.