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

question 4

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.

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