Sex Linked Inheritance Practice Problems
Name:_______________________P___
**In fruit flies, eye color is a sex linked trait. Red is dominant to white.**
1. What are the sexes (M/F) and eye colors (Red/White) 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 purebred red eyed female and a white eyed male:
What are the genotypes of the parents:
___________ and _______________
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?
___________ and ________________
white eyed, male _______%
white eyed, female _______%
red eyed, male _______%
red eyed, female _______%
6. Math: What if in the above cross, 100 males were produced and 200 females. How many total red-eyed flies would we
expect there to be? ________
X-Linked Genetics in the Calico Cat (X-Inactivation)
The coloration of calico cats is the result of the inactivation of one of a female cat's sex
chromosomes. In females, two X chromosomes are present in all cells but only one is active, the
inactive one is called a BARR BODY. This is why the coat color is random. Calico is a coat
color found in cats, which is caused by a SEX-LINKED, CODOMINANT allele.
B = Black
R = oRange
BR = calico
Show each of the crosses below and include the phenotypic percentages of the offspring.
7. A black male crossed with an orange female
______% orange females
______% orange males
______% black females
______% black males
______% calico females
8. An orange male crossed with a calico female
______% orange females
______% orange males
______% black females
______% black males
______% calico females
9. A black male crossed with a black female
______% orange females
______% orange males
______% black females
______% black males
______% calico females
10. An orange male crossed with an orange female
______% orange females
______% orange males
______% black females
______% black males
______% calico females
11. A black male crossed with a calico females
______% orange females
______% orange males
______% black females
______% black males
______% calico females
12. If you are a cat breeder, what type of parents should you choose to have the MOST number of calico kittens?