Psyc 3102 (Fall 2004): Problem Set:

Mendel & Punnett Rectangles

1) For the ABO blood system, what are the predicted genotypes and the phenotypes and their frequencies for the offspring of the following matings: See the Applet "Offsrping from the matings on the ABO blood group" for more examples.

          1.a) AA x AB

          1.b) AO x OO

          1.c) AB x OO

          1.d) AO x BO

          1.e) AB x AO

2) The MN blood group is another system due to a single gene with two codominant alleles, M and N. Codominant means that the phenotype for the heterozygote is MN. Give the expected frequency and genotypes from the following matings:

          2.a) MM x NN

          2.b) MN x NN

          2.c) MN x MN

3) Remember the hemoglobin molecule? It carries oxygen through the blood. Although the genetics are somewhat complex, we will simply consider two alleles for this molecule, A and S. Genotype AA has normal hemoglobin but has little resistance to malaria, genotype AS also has normal hemoglobin but has resistance to malaria, and genotype SS has abnormal hemoglobin and little resistance to malaria. (Genotype SS would develop what is called sickle cell anemia.) Give the genotypes and the phenotypes for both hemoglobin and malarial resistance for the following matings:

          3.a) AA x AS

          3.b) AS X AS

          3.c) Assume that genotype SS is lethal (i.e., people die before they reach reproductive age). What is the only type of mating that can produce an SS offspring?

4) Monoamine oxidase A deficiency (MAOAD) is an X-linked recessive disorder.  There are three alleles for this locus: the dominant allele A creates normal monoamine oxidase. The two recessive alleles, a and a*, produce the deficiency. Genotype aa* will also have the deficiency. Give the expected outcomes for offspring as a whole and for the male and female offspring separately for the following matings:

          4.a) Female with Aa and male with A

          4.b) Female with Aa* and male with a?

          4.c) Male with a* and female with AA?

5) Hemophilia is an X-linked, recessive disorder.  Let HX1 denote the normal allele and HX2 denote the recessive allele that causes hemophilia.  Give the offspring genotypes, phenotypes, and their frequencies from the following matings:

          5.a) Female (HX1,HX2) and male (HX1)

          5.b) Female (HX1,HX2) and male (HX2)

          5.c) Male (HX2) and female (HX1,HX1)

6) Suppose that allele A1 contributes +1 to a quantitative phenotype, allele A2 contributes +2 to the phenotype, and allele A3 contributes +3.  What are the expected genotypes and phenotypes of the offspring from the following matings?

7) Suppose that allele B1 contributes 1 to the phenotype, allele B2 contributes 2 to the phenotype and allele B3 contributes 3 to the phenotype.  Allele B3, however, is dominant to allele B1.  That is, the genotype B1B3 has the same phenotype as genotype B3B3 (6).  What are the expected genotypes and phenotypes from the following matings?