Genetics: X Linked Genes
Name:
Date:
***In fruit flies, eye color is a sex linked trait. Red is dominant to white***
1. What are the sexes and eye colors of the flies with the following genotypes?
XR Xr ____________
XR XR ____________
XR Y ____________
Xr Y ____________
Xr Xr____________
2. What are the genotypes of the following fruit flies?
white eyes, male ________
white eyes, female ________
red eyes, female (heterozygous) ________
red eyes, male ________
3. Use a Punnett square to show the cross of a white eyed female
male XR
Xr Xr with a red-eyed
Y.
4. Show a cross between a pure red-eyed female and a white-eyed male.
What are the genotypes of the parents? __________ x __________
How many offspring are:
white-eyed, male ______
white-eyed, female ______
red-eyed, male ______
red-eyed, female ______
5. Show the cross of a red-eyed female (heterozygous) and a red-eyed male.
What are the genotypes of the parents? __________ x __________
How many offspring are:
white-eyed, male ______
white-eyed, female ______
red-eyed, male ______
red-eyed, female ______
In humans, hemophilia is a recessive, X-linked trait. Females can be normal, have the
disease, or be carriers of the trait. Males will either have the disease or not, but they won’t
ever be carriers. Genotypes are shown below.
XH XH = female, normal
XH Xh = female, carrier
Xh Xh = female, hemophiliac
XH Y = male, normal
Xh Y = male, hemophiliac
6. Show the cross of a man who has hemophilia with a woman who is a carrier. What is the
probability that their children will have the disease? _________
7. A woman who is a carrier marries a normal man. Show the cross. What is the probability
that their children will have hemophilia? __________ What sex will a child of theirs with
hemophilia be? ___________
8. A woman who has hemophilia marries a normal man. Show the cross. How many of
their children will have hemophilia, and what is their gender?
Calico is a color found on cats, which is caused by a sex-linked, codominant allele.
XB XB, orange XR XR,
Male cats con only be: black XB Y
or orange XR Y
Female cats can be:
black
or calico
9. Show the cross of a female calico cat with a black male.
How many of the kittens will be black & male? _____
How many of the kittens will be calico & female? _____
How many of the kittens will be calico & male? _____
10. Show the cross of a female black cat with a male orange cat.
How many of the kittens will be calico and female? _____
What color will all the male cats be? _______
XB XR