Solutions For An Introduction to Genetic Analysis Chapter 4 Problem 31P

a) To determine, whether these genes are linked, we need to observe and see the results of the testcross are seen in the progeny.

The progeny can also be written with the genotypes as:

• 116 – shrunken, white – s/s ; w/w ; y⁺/-

• 4 – wild type – s⁺/- ; w⁺/- ; y⁺/-

• 2538 – shrunken – s/s ; w⁺/- ; y⁺/-

• 601 – shrunken, waxy - s/s ; w⁺/- ; y/y

• 626 – white - s⁺/- ; w/w ; y⁺/-

• 2708 – white, waxy - s⁺/- ; w/w ; y/y

• 2 – shrunken, white, waxy - s/s ; w/w ; y/y

• 113 – waxy - s⁺/- ; w⁺/- ; y/y

Total – 6708

The crossovers between white and shrunken are:

• s⁺/- ; w⁺/-

• s/s ; w/w -

• s⁺/- ; w/w -

• s/s ; w⁺/- -

Since, the 1:1:1:1 ratio is not seen, these genes are linked.

The crossovers between shrunken and waxy are:

• s⁺/- ; y⁺/-

• s⁺/-; y/y -

• s/s; y⁺/- -

• s/s ; y/y -

Since, the 1:1:1:1 ratio is not seen, these genes are linked.

The crossovers between white and waxy are:

• w⁺/- ; y⁺/-

• w⁺/-; y/y -

• w/w ; y⁺/-

• w/w ; y/y -

Since, the 1:1:1:1 ratio is not seen, these genes are linked.

The crossovers between white and shrunken are:

• s⁺/- ; w⁺/- 113 + 4

• s/s ; w/w – 116 + 2

Total: 235

The crossovers between shrunken and waxy are:

• s⁺/- ; y⁺/- 626 + 4

• s/s ; y/y – 601 + 2

Total: 1233

The gene distances can be determined in this way:

Between white and shrunken:

Between shrunken and waxy:

The map distances are shown:

b) The allele arrangement on the chromosomes of the triple heterozygote used in the test cross:

s ⁺ /s; w ⁺ /w; y ⁺ /y x s/s ; w/w ; y/y

c) Interference can be calculated based on the formula: