Solutions For An Introduction to Genetic Analysis Chapter 4 Problem 68P

In contrast, there is no occurrence of crossing over in 88% of meioses in region (i) and a single crossover occurs in the remaining 12%. In region (ii), no crossover occurs in 80% of meioses and a single crossover occurs in 20% of meioses.

The percentage of tetrads without crossing over is calculated in the following way:

The percentage of tetrads with a single crossover in region (i) and no crossover in region (ii) can be calculated in this way:

The percentage of tetrads with a single crossover in region (ii) and no crossover in region (i) can be calculated in this way:

The percentage of tetrads with crossovers in both region (i) and (ii) would be calculated in this way:

The pattern of segregation that result for each case:

For no crossovers in both regions:

For a single crossover in region (i):

For a single crossover in region (ii):

For double crossovers, there are 4 types:

Two-strands:

Four-strands:

Three-strands in two different ways:

a) M_IM_IPD is the result of no crossovers in either region (i) or (ii). This is calculated as 70.4%.

b) M_IM_I NPD is not found, as a result.

c) M_IM_II T is a result of a single crossover in region (ii). This is calculated as 17.6%.

d) M_IIM_I T is a result of two and four-strand double crossovers. This is calculated as 1.2%.

e) M_IIM_IIPD is a result of a single crossover in region (i). This is calculated as 9.6%.

f) M_IIM_II NPD is not found, as a result.

g) M_IIM_II T is the result of both three-strand double crossovers. This is calculated as 1.2%.