Problem B: Prairie Dog Population Genetics A relatively stable population of Bla

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Problem B: Prairie Dog Population Genetics
A relatively stable population of Black-footed Prairie Dogs (70,000 individuals) lives in a national park in
Saskatchewan, Canada. These creatures have various tones of brown fur, but may have brown or auburn tails.
Furthermore, tails may be of solid color (brown or auburn) or be tipped with white or black fur. Three alleles for
tail coloration exist in this population. These alleles include:

Tail has black fur at tip. Codominant with T*; recessive to T

The frequency of the (T) allele in this population is 0.28, and the frequency of the (t) is 0.4.
Answer each of the following. Show all of your work/calculations. Cite your rationale if appropriate.

1. List and describe all the possible genotypes and their respective phenotypes for this gene system in the
population.

2. Using the Hardy-Weinberg theorem, calculate the probable frequency of animals with the following
phenotypes in this population:
• White tipped tails
• Black tipped auburn tails

3. What is the expected combined frequency of individuals carrying the TT, TT* and Tt genotypes in this
population?

4. How many (number, not percentage) of the prairie dogs would you expect to have black tipped, auburn
tails? Explain.

5. In a different population of 10,000 prairie dogs (South Dakota, USA), only the T and t alleles are found. If
this group included only 400 animals with black tipped, brown tails, what is the probable number (not
frequency) of individuals that are homozygous dominant (TT) in this herd?

Allele Trait Notes on Phenotype and Relationship to other Alleles T White Tip Tail has white fur at tip. Completely dominant over t; codominant with T* t Black tip

Tail has black fur at tip. Codominant with T*; recessive to T

T* Auburn tail Background tail color is auburn when T* is present. Codominant with T or t

Explanation / Answer

1) There are 6 possible genotypes. Their respective phenotypes are described below,

TT - tail has white fur at tip

Tt - tail has white fur at tip

TT* - background tail color is auburn

tt - tail has black fur at tip

T*t - background tail color is auburn

T*T* - background tail color is auburn

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