Three traits have been identified in a population.
- The Tall gene in its recessive allele (x) is responsible for excessive height.
- The Brownie gene has a recessive allele (y) which gives rise to brunette hair color, the dominant allele (Y) being responsible for blonde hair color.
- In the Cee gene the double vision allele (D) is dominant to the normal vision allele (d), but the homozygous DD genotype is embryonically lethal.
A cross of two triple heterozygotes for the above genes occurs to produce an F1 generation. Disregarding issues of incest in relationships or matings in the F1 generation answer the following questions. The three traits are inherited independently of each other (i.e. there is no linkage).
Begin this assignment by drawing a Punnet Square, or diagrams of crosses which you should submit with your answer. For the Tall and Brownie genes dominant alleles are denoted with a capital letter and recessive alleles with lower case letters.
Your answers must include a clear and reasoned explanation describing how you have arrived at the numerical answers. A probability, ratio or percentage value alone is insufficient.
Note: The lethal combinations (DD) should be excluded from your calculations.
- Punnet square (computer generated; hand-drawn is unacceptable). [3pts]
- What is the probability of a person in the F1 generation having the genotype XXYYdd? [2pts]
- What is the probability of a person being blonde haired and normal height with double vision? [3pts]
- What is the probability of a non-parental combination of alleles arising in a person of the F1 generation? [2pts]
- Relationships occur within the F1 generation. Individuals with normal vision want to avoid tall partners. What is the probability of an individual with the XXYYdd genotype finding a normal height partner who does not have his own genotype? Ignore issues of gender. [3pts]
- Double-visioned, tall individuals in the F1 generation are having problems finding a match and a singles party is organized for them. Assuming all of this group go along what are the possible genotypes of the party-goers? What is the probability of someone at the party being blonde? [4pts]
- Outline three differences between mitotic division and meiotic division. [3pts]