Question

In and interrupted mating experiment, it is seem that the after 10 mins Azi^R gene in recipient, after 20 minuites there is appearance of ton^R  and after 15 mins the recipient is lac^+ , but the recipient is almost never his^+.  Where in the genome is the ori of transfer?

(a) Between Azi^R and Ton^R genes

(b) Between Ton^R and Lac^+

(c) Between Lac^+ and His^+

(d) Between His^+ and Azi^R

I had been asked this question during an interview for a job.

This is a very interesting question from Gene Mapping in Bacteria by Conjugation topic in section Genomics : The Mapping and Sequencing of Genomes of Cytogenetics

Answer 1

Right answer is (d) Between His^+ and Azi^R

The best explanation: As the origin of transfer is between His^+ and Azi^R the sequence follows Azi^R, ->Ton^R->Lac^+->His^+ or the reverse direction. Thus, longer time is required for His to enter and in most cases before that the conjugation tube breaks.