Genetics - Worksheet #9 Sex-linkageProblems

Name ____________________________________ Date__________ Class_____

Make sure that you show the crosses for each problem.Make sure you include a key telling what letters you are using forexample: H is normal and h is hemophiliac. Remember this is sex-linked so you must show sex chromosomes. Use the foilmethod.

1. Color blindness in humans is sex-linked and recessive. Anormal man marries a woman whose father was colorblind but she wasnot.  

Cross:

Show the genotypes:

the man

his wife,

the genotypes and phenotypes of theiroffspring.

2. A man with normal vision marries a woman who also hasnormal vision. One of their childrenis      

     colorblind.  

    

   Cross:

Genotypes of the man

Genotype of woman ,  

genotype of their child.

3. Hemophilia is caused by a recessive gene on the Xchromosome.  

    A woman whose father was ahemophiliac but who is not one herself marries a normalman.  

Cross:

What are their genotypes and what are the possiblegenotypes and phenotypes of their children? What percentage oftheir daughters could be expected to be hemophiliac:

expected to be carriers;

what percentage of their sons will be

hemophiliac: carriers?

4. In cats, certain colors are sex linked. These genesalso display incomplete dominance. Use Yfor     

      yellow and B forblack. Tortoise shell color (Calico) is the combination of both Yand B.  

Cross a tortoise shell female with a blackmale.

Coss:

Genotypes of offspring:

Phenotypes possible for their offspring.

Why are tortoise shell cats always female?

5. In fruit flies, straight wings is dominant overcurved wings. A certain male was mated to a female with curvedwings. They produce 50% straight and 50% curved-wingedoffspring.  

What are the genotypes for the male,

                                        thefemale

                              andtheir offspring.