In humans pattern baldness is a sex-influenced trait, whose degree of expression is controlled by the sex of the individual, such that it is autosomal dominant in males while autosomal recessive in females. On the other hand, colour blindness and haemophilia are both
recessive X-linked traits.
B = bald; b = non-bald; C = normal vision; c = colour blind; H = normal blood clotting; h = haemophilia.
a. Give the genotypes for individuals in the P and F1 generations for the matings below. Assume that no crossing over has occurred.
Mating 1
P: bald, non-colour blind, non-haemophiliac female X non-bald, colour blind, haemophiliac male
F1: bald, colour blind, haemophiliac male
Mating 2
P: bald, colour blind, non-haemophiliac female X bald, non-colour blind, haemophiliac male
F1: non-bald, non-colour blind, non-haemophiliac female
b. Suppose that the male and female from the F1s marry, what are the probabilities of the male and female offspring outlined below?
i. haemophiliac but otherwise normal
ii. colour blind and haemophiliac but normal for baldness
iii. colour blind but otherwise normal
iv. bald, colour blind and haemophiliac
7 answers