You have infected E. coli cells with two strains of T4 virus. One strain is minu

Question

You have infected E. coli cells with two strains of T4 virus. One strain is minute (m), rapid lysis (r), and turbid (tu); the other is wild type for all three markers. The lytic products of this infection are plated and classified. The resulting 10,341 plaques were distributed among eight genotypes is shown in the table above. What is the coefficient of coincidence in the cross? (Hint: solve this like a normal 3 point cross)

Question 10 options:

-0.93

-0.25

-0.4

0.4

0.64

1.2

1.25

Please explain!!

-0.93

-0.25

-0.4

0.4

0.64

1.2

1.25

Explanation / Answer

1.2

The coefficient of coincidence (c.o.c.) compares the actual number of double crossovers to the expected number, (where c.o.c. = observed double crossovers/expected double crossovers). For these data, the expected number of double recombinants is (0.128)(0.208)(10,342) = 275. Thus, c.o.c. = (162 + 172)/275 = 1.2. This indicates that there are more double crossover events than predicted and suggests that the occurrence of one crossover makes a second crossover between the same DNA molecules more likely to occur.

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