Jacob and Colleagues Developed a Time- Of- Entry Mapping Technique

Multiple Choice

Jacob and colleagues developed a time- of- entry mapping technique. They used the genes for threonine and leucine synthesis (thr and leu) , which are near the oriT site, as selected markers. Additionally, they used an E. coli F- strain P678 that has dysfunctional variants for all of the genes studied. They also used an HfrH strain that carried a functional allele for all genes studied. Which of the following statements is FALSE regarding the time- of- entry profile they acquired?

A) The azi gene is closer to the thr and leu genes than the ton, lac, and gal genes.
B) The ton gene is found between the azi and lac genes.
C) Had the experiment continued, a time of entry map could be viewed for the entire E. coli chromosome.
D) The lac+ allele appears at about 16 or 17 minutes.
E) At 40 minutes, nearly 20% of exconjugants screened for the selected markers have the gal allele.