Practice Problems for Codominance, Incomplete Dominance and Sex Linked Traits

Practice Problems for Codominance, Incomplete dominance and Sex Linked Traits

1.  In the Oligio family, one parent has Type A blood, the other has Type B. They have 4 children: one with Type A, one with Type B, one with Type AB and one with Type O blood. What are the genotypes of the people in this family?

1. Parent 1 ______

1. Parent 2 ______

1. Child 1 ______

1. Child 2 ______

1. Child 3 ______

1. Child4 ______

2.  In a recent case in Spokane Washington, a young woman accused a soldier of being the father of her child. The soldier denied the accusation. The soldier’s lawyer demanded that all three parties submit to a blood type. The mother was found to be Type A, the child Type AB and the father Type O.

1. What are the genotypes of the three people involved?

1. Could the soldier be the father?

3.  It was suspected that two babies had been exchanged at the hospital. Mr and Mrs Jones received baby#1 and Mr and Mrs Simon received Baby #2. Blood tests on the parents and babies revealed the following:

Mr Jones Type A
Mrs Jones Type O / Mr Simon Type AB
Mrs Simon Type O
Baby #1 Type A / Baby #2 Type O

Were the babies switched? What is the evidence for your answer?

4.  A woman has a daughter. There are three men whom she claims might be the father. The judge in the paternity suit orders blood typing for all the involved parties. The mother is Type A, the daughter is type O. Man #1 is Type AB, Man #2 is Type B and Man #3 is Type O. The mother claims that man #3 must be the father.

1. Is she correct? Explain your answer.

1. The judge isn’t satisfied so he asks for the medical records of the parties involved. He discovers that the little girl is colorblind. Man #1 and Man #2 are also colorblind. Man #3 and the mother are not colorblind. So who might be the father?

5.  Marian’s father is colorblind, as is her maternal grandfather (her mother’s father). Marian has normal vision. Marian and her husband Ned, who is colorblind, have just had their first child, a son they named Mickey.

1. What are the genotypes of Marian and Ned

1. What are all the possible genotypes of their children?

1. What is the probability that their son will be colorblind?

1. If Ned were not colorblind, how would this affect the probability that Mickey would be colorblind?

6.  In cats there is a coat color gene on the X chromosome. The two alleles are orange and black. If the cat is heterozygous for the gene, its coat color will be tortoiseshell (a splotchy mix of orange and black). Predict the genotype and phenotypes and the frequencies of each for the following crosses.

1. Black female and orange male

1. Orange female and black male

1. Tortoiseshell female and black male

1. Tortoiseshell female and orange male

1. Can a tortoiseshell male exist?