110. Suppose a single gene determines whether the coloring of a certain animal is dark or light. The coloring will be dark if the genotype is either AA or Aa and will be light only if the genotype is aa (so A is dominant and a is recessive).

Consider two parents with genotypes Aa and AA. The rst contributes A to an offspring with probability and a with probability , whereas the second contributes A for sure. The resulting offspring will be either AA or Aa, and therefore will be dark colored. Assume that this child then mates with an Aa animal to produce a grandchild with dark coloring. In light of this information, what is the probability that the rst-generation offspring has the Aa genotype (is heterozygous)? Hint: Construct an appropriate tree diagram.