NAME: _____________________________ PERIOD:_________

 

DATE:____________________ DATE DUE:_________________

 

SEX-LINKED TRAITS

 

 

1. In humans, red-green color-blindness is a sex-linked trait located on the X chromosomes.  Normal vision (XN) is dominant to color-blindness (Xn). Using a Punnett square, cross a heterozygous female with a male that has normal vision.

 

__________ X __________

 

 

 

 

 

 

 

 

 

 

 

 

a. What is the genotypic ratio of the possible offspring?

 

 

b. What is the phenotypic ratio of the possible offspring?

 

 

Using a Punnett square, cross a heterozygous female with a male that has color-blindness.

 

 

__________ X __________

 

 

 

 

 

 

 

 

 

 

 

 

 

 

a. What is the genotypic ratio of the possible offspring?

 

b. What is the phenotypic ratio of the possible offspring?

 

c. What is the probability (chance) that this couple will have a child that is color-blind?

 

d. What is the probability that if this couple has a daughter, she will carry the color-blind gene but not be colorblind herself?

 

3. In humans, hemophilia is a sex-linked trait located on the X chromosome. Normal blood is dominant (XH) to hemophilia (Xh).  A heterozygous female is referred to as a carrier.  Using a Punnett square, cross a female with hemophilia with a normal male.

 

 

__________ X __________

 

 

 

 

 

 

 

 

 

 

 

 

 

a. What is the genotypic ratio of the possible offspring?

 

b. What is the phenotypic ratio of the possible offspring?

 

c. What percentage of this couple’s sons will have hemophilia?

 

d. What percentage of this couple’s daughters will have hemophilia?

 

4. Using a Punnett square, cross a carrier female with a male with hemophilia.

 

 

__________ X __________

 

 

 

 

 

 

 

 

 

 

 

 

a. What is the genotypic ratio of the possible offspring?

 

b. What is the phenotypic ratio of the possible offspring?

 

c. What percentage of this couple’s sons will have hemophilia?

5. Duchenne’s muscular dystrophy is a sex-linked trait located on the chromosome. Muscular dystrophy causes muscular weakness but is recessive (Xd) to normal muscle tone (XD). Using a Punnett square, cross a carrier female with a male that has Duchenne’s muscular dystrophy.

 

__________ X __________

 

 

 

 

 

 

 

 

 

 

 

 

a. What is the genotypic ratio of the possible offspring?

 

b. What is the phenotypic ratio of the possible offspring?

 

c. What percentage of this couple’s sons will have muscular dystrophy?

 

d. What percentage of this couple’s daughters will have muscular dystrophy?

 

6. Using a Punnett square, cross a carrier female with a male that has normal muscle tone.

 

__________ X __________

 

 

 

 

 

 

 

 

 

 

 

 

 

 

a. What is the genotypic ratio of the possible offspring?

 

b. What is the phenotypic ratio of the possible offspring?

 

c. What percentage of this couple’s sons will have muscular dystrophy?

 

d. What percentage of this couple’s daughters will have muscular dystrophy?