You infect E. coli cells with two strains of phage ?. One strain has a mutant ho

Question

You infect E. coli cells with two strains of phage ?. One strain has a mutant host range, produces larger-than-normal plaques, and is temperature sensitive (genotype: h r t ). The other strain expresses the wild-type phenotype for these characters. Progeny phages from the lysed E. coli cells are collected and plated on a lawn of bacteria. You observe the following number of plaques for each progeny phage phenotype (which directly corresponds to its genotype): Progeny phage genotype Number of plaques h+ r+ t+ 562 h r t 578 h+ r t 41 h r+ t+ 35 h+ r t+ 88 h r+ t 75 h+ r+ t 6 h r t+ 5

You want to find out whether the formation of a crossover in one region interferes with the formation of a crossover in the other region. To calculate the extent of interference, you will first need to figure out the coefficient of coincidence. To determine the coefficient of coincidence, you will need to divide the observed number of double crossovers by the expected number of double crossovers.

How many double crossover events do you expect given your answers above? Please round to the nearest whole number.

0.01

Incorrect

Explanation / Answer

Number of Double Crossovers calculations

Interference (I) = 1-C

C(coefficient of coincidence)= observed number of double crossovers/expected number of double crossovers.

= 3/8= 0.375 =0.38

Interference (I) = 1-C = 1-0.38= 62 or 62%

This means that 62% of the expected number of crossovers did not occur

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