Genetics Problems

1) In humans, hemophilia is caused by an X-linked recessive gene. A woman who is a nonbleeder had a father who was a hemophiliac. She marries a nonbleeder, and they plan to have children. Calculate the probability of hemophilia in the female and male offspring.

2) Colour-blindness is a sex-linked recessive trait. If a man who is colour-blind marries a woman who is homozygous dominant for color blindness, what is the proability that they will have children who are:

a) colour-blind males.

b) carrier females.

c) colour-blind females.

3) In humans the three alleles I^A, I^B, and I^O constitute a multiple allelic series that determine the ABO blood group system. For the following problems, state whether the child mentioned can actually be produced from the marriage.

a) An O child from the marriage of two A individuals

b) An O child from the marriage of an A to an O.

c) An AB child from the marriage of an A to an O.

d) An O child from the marriage of AB to an A.

e) An A child from the marriage of an AB to a B.

4) In Shorthorn cattle the heterozygous condition of the alleles for red coat color (C^R) and white coat color (C^W) is roan coat color (a mix of red and white coat color produced by incomplete dominance). If two roan cattle are mated, what proportion of the progeny will resemble their parents in coat color?

5) What progeny will a roan Shorthorn have if bred to a white Shorthorn?

6) A genetic researcher in Paraguay was working on a Guinea pig ranch; Yippee Yie Yay! He crossed a black pig with an albino pig. He obtained 12 black offspring. He then crossed a second set of different pigs, one black and one albino. Out of 11 offspring, 6 were black and 5 were albino. List the likely genotypes of the parents in each case.

7) A man and his female significant other are both heterozygous for brown eyes. They are quite wealthy and know nothing about overpopulation, and so have six children, all of whom have blue eyes. How is this occurrence explained? What are the chances that their next child will have blue eyes?

8) What is the expected phenotypic ratio of children from parents with the following blood genotypes: I^A I^A and I^B i?

9)

Tribbles are hypothetical animals that look like this à

The trait, bald (f), is recessive to furry (F) and the trait, long leg (s), is recessive to short leg (S). If a homozygous, furry short legged tribble mates with a homozygous bald long legged tribble, what will be the genotypes and phenotypes of the tribble F₂ generation?