AUTOSOMAL TRAITS: 

1. In Mendel’s peas, yellow seed color is dominant to green.  Find phenotype and genotype probabilities for each of the following pea plant crosses:

a) yellow (homozygous) + green
b) yellow (heterozygous) + green
c) yellow (heterozygous) + yellow (homozygous)
d) yellow (heterozygous) + yellow (heterozygous)


2. How would it be possible for two parents who have free-hanging earlobes (dominant) to have a child without this characteristic?  


3. In the Smith family, the father is the only one who can roll his tongue (dominant).  The mother and all the children cannot (recessive).  What is the genotype of Mr. Smith?


4.  In a hypothetical population of rabbits, a black coat is dominant to a brown coat.  If two black rabbits mated (each having heterozygous genotypes), what would be the phenotype ratios of their offspring?  

SEX-LINKED TRAITS:

5.      The gene that produces blood clotting in humans is located on the X chromosome.  The dominant allele results in normal blood clotting, the recessive allele results in no clotting (hemophilia).  John has hemophilia, but his wife Nancy doesn’t (nor is she a carrier/heterozygous).  Is it possible for them to have a daughter with the disease?  How about a son?  

6.   A woman with Red-green colorblindness (a recessive disorder) marries a man without it.  Assume you’re a genetics counselor, and this couple wants to find out the likelihood of having a child with the Red-green colorblindess.  What would you tell them?