Name:_____________________________________

**In fruit flies, eye color is a sex linked trait. Red is dominant to white.**

1. What are the sexes and eye colors of flies with the following genotypes?

X R X r _________ X R Y __________ X r X r __________

X R X R ____________ X r Y ____________

2. What are the genotypes of these flies:

white eyed, male ____________ red eyed female (heterozygous) ________

white eyed, female ___________ red eyed, male ___________

3. Show the cross of a white eyed female X r X r with a red-eyed male X R Y .

4. Show a cross between a pure red eyed female and a white eyed male. What are the genotypes of the parents:

___________ and _______________

How many 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?

___________ & ________________

How many are:

white eyed, male ____ white eyed, female ____ red eyed, male ____ red eyed, female ____

Math: What if in the above cross, 100 males were produced and 200 females. How many total red-eyed flies would there be? ________

6. In humans, hemophilia is a sex linked trait. Females can be normal, carriers, or have the disease. Males will either have the disease or not (but they wont ever be carriers)

X h Y= male, hemophiliac

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 in the family with hemophilia be?

8. A woman who has hemophilia marries a normal man. How many of their children will have hemophilia, and what is their sex?

9. In cats, the gene for calico (multicolored) cats is codominant. Females that receive a B and an R gene have black and oRange splotches on white coats. Males can only be black or orange, but never calico.

Heres what a calico females genotype would look like: X B X R

Show the cross of a female calico cat with a black male?

What percentage of the kittens will be black and male? _________ What percentage of the kittens will be calico and male? _________ What percentage of the kittens will be calico and female? _________

10. Show the cross of a female black cat, with a male orange cat.

What percentage of the kittens will be calico and female? _____What color will all the male cats be? ______

Visit link:
Genetics - X Linked Problems - The Biology Corner

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