Biology 207 - Practice questions 5 - Mendelian genetics
Question 1 Type I albinism is caused by the absence of the enzyme Tyrosinase which
converts the amino acid tyrosine into the pigment melanin. This enzyme is encoded by the
TYR gene at 11q14-q21.
a) Describe the gene's cytologtical location.
b) Why are mutant alleles of this gene recessive?
Question 2 Both members of an Edmonton couple are heterozygous for recessive mutations
in the TYR gene. They have two children.
a) Write out the genotype and phenotype for each parent.
b) What are the possible genotypes of the gametes, and their frequencies,
produced by the father? The mother?
c) What is the probability that the first child is albino?
d) What is the probability that the second child is albino?
e) What is the probability that both children are albino?
f) What is the probability that both children are phenotypically identical with regard
to skin color?
g) What is the probability that both children will be genetically identical at that
Question 3 You