Question

Genetics: will give a thumbs up if correct. Please show work. Thank you.

1. Red/green color blindness is controlled by an X linked gene. A normal man and women marry. The fathers of both of these individuals are color blind but the mothers of both are homozygous normal. The probability that their first child will be color blind is:

a. 1/2

b. 1/3

c. 1/4

d. 1/8

e. 0

2. If you cross a Gg (G= yellow, g=green) Ww (W=round, w=wrinkled) individual with a ggWw individual what would be your expected phenotype ratio.

a. 3:3:1:1

b. 9:3:3:1

c. 7:4:3:2

d. 1:1:1:1

e. 9:7

Answer 1

Answer 1. 1/4 is correct answer.

Color blindness is a X-linked recessive disease, therefore it is expressed only in males. Female having defected X chromosome have normal vision and act as carrier of disease. According to given situation father of both husband and wife are color blind, as shown in figure husband do not have defected X chromosome but wife is a carrier, having defected X chromosome.

Ptobability of their 1st child having the disease is therefore 25% or 1/4 because other three will not have disease.

Answer 2