Problem

Solutions For An Introduction to Genetic Analysis Chapter 4 Problem 14P

Step-by-Step Solution

Solution 1

The distance between the R and S loci is 35 m.u. apart. When a plant with a genotype of RS/rs is selfed, the phenotype of the progeny and their proportions can be calculated in this way:

Parents are

Gametes	Proportion
R S	1/2 (1 – 0.35) = 0.326
r s	1/2 (1 – 0.35) = 0.326
R s	1/2 (0.35) = 0.176
r S	1/2 (0.35) = 0.176

So, each gamete pair has enough proportion of distance.

Step #2 of 3

The gametes are crossed in F1 generation, for which 10 combination of genotypes are formed. Now, calculate F1 genotypes for each combination in following manner:

Gametes	Proportion
RS/RS	0.325 x 0.325 = 0.1056
rs/rs	0.325 x 0.325 = 0.1056
rs/rS	2 x (0.325 x 0.175) = 0.1138
rs/Rs	2 x (0.325 x 0.175) = 0.1138
RS/rS	2 x (0.325 x 0.175) = 0.1138
RS/Rs	2 x (0.325 x 0.175) = 0.1138
RS/rs	2 x (0.325 x 0.325) = 0.2113
Rs/Rs	0.175 x 0.175 = 0.0306
rS/rS	0.175 x 0.175 = 0.0306
Rs/rS	2 x (0.175 x 0.175) = 0.0613

Step #3 of 3

Now, calculate proportion of F1 phenotypes in the following manner:

Gametes	Proportion
RS	0.1056 + 0.1138 + 0.1138 + 0.2113 + 0.0613 = 0.6058
rs	0.1056
Rs	0.1138 + 0.0306 = 0.1444
rS	0.1138 + 0.0306 = 0.1444

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