In five Hfr strains, each of which was used to build a time-of-entry map, the genes entered the recipient cells as follows: Strain 1: S L A C T F
Strain 2: N P F T C A
Strain 3: T F P N U Y
Strain 4: S H Y U N P
Strain 5: U N P F T C
Which of the following represents a correct compilation of these results?
A)S L A C T F P N H C U
B)N P F T S L A C H U T
C)T C A L S P N U Y H
D)U N P F T C A L S T F
E)S L A C T F P N U Y H

Question

Quizplus · Accepted Answer

Each strain entered the recipient cells in a specific order, as shown by the letters indicating the genes. To compile a correct time-of-entry map, we need to combine these orders in a way that makes sense. Starting with strain 1, we see that it enters as S L A C T F. Strain 2 enters as N P F T C A, but we notice that it shares the gene order F T C with strain 1. Similarly, strain 3 enters as T F P N U Y, sharing the genes F and N with strains 1 and 2. Strain 4 enters as S H Y U N P, sharing genes S and N with strains 1 and 2, and strain 5 as U N P F T C, which shares the genes N, P, F, and T with the previous strains.

By combining these orders, we can build a time-of-entry map that includes all the genes. The correct order for the genes is: S L A C T F P N U Y H. This order starts with the genes from strain 1, then adds the unique genes from each subsequent strain. The correct choice is therefore E.

In Five Hfr Strains, Each of Which Was Used to Build