1. Parental generation X F 1 generation F 2 generation Number of each phenotype Phenotypes 1 6 15 20 15 6 1 Figure 10.20a Kernel color is quantitative trait.

2. aa bb cc (pure line white) X AA BB CC (pure line red) Aa Bb Cc (medium red) Self-fertilization 20 2 AABbcc 2 AaBBcc 8 AaBbCc 2 aaBbCC 2 aaBBCc 2 AabbCC 2 AAbbCc 15 4 AABbCc 4 AaBBCc 1 aaBBCC 4 AaBbCC 1 AAbbCC 1 AABBcc 2 AABbCC 2 AaBBCC 2 AABBCc 6 1 AABBCC 15 4 AaBbcc 4 aaBbCc 1 aabbCC 4 AabbCc 1 aaBBcc 1 AAbbcc 2 aabbCc 2 aaBbcc 2 Aabbcc 6 1 aabbcc 1 0123456 Number of red pigment alleles (A, B, or C) in genotype 1 Figure 10.20b Model to explain inheritance of kernel color

3. Predict the phenotype frequencies of a cross between AaBb x Aabb Assume the A locus and B locus are on different chromosomes

4. Two genes, each with two alleles, are known to influence coat color in Labrador retrievers. Let’s call the alleles for the first gene B and b and E and e for the second gene. The ratio of colors is 9 black: 3 chocolate: 4 yellow. 1. Suggest a mechanism for inheritance of coat color 2. Write out all possible genotypes and describe the phenotype of each genotype.

5. Penetrance The percentage of individuals with a given genotype who exhibit the phenotype associated with that genotype

6. Pedigree showing incomplete penetrance

7. Reasons for incomplete penetrance Epistatic genes, pleiotropic genes or other genes which suppress the expression of the genotype

8. Expressivity The degree to which a genotype is expressed in the phenotype

9. Expressivity in beagles Each of these dogs has the dominant allele for piebald (black and white) spotting The degree of spotting varies among individuals

10. Polydactyly

11. Penetrance and expressivity

12. Environmental effects on fur color in Himalayan rabbits

13. Fur color in Siamese cats