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Analyzing a gene and manipulating phenotypes and allels to predict desired outcomes. Attachments in MS Word.

Fur colour in the babbit, a furry little animal and popular pet, is determined by a pair of alleles, B and b. B/B and B/b babbits are black, and b/b babbits are white. A farmer wants to breed babbits for sale. True breeding white (b/b) female babbits breed poorly. The farmer purchases a pair of black babbits, and these mate and produce six black offspring and two white offspring. The farmer immediately sells his white babbits, and then comes to consult you for a breeding strategy to produce more white babbits.

a. If he performed random crosses between pairs of F1 black babbits, what proportion of the F2 progeny would be white?

b. If he crossed an F1 male to the parental female, what is the probability that this cross will produce white progeny?

c. What would be the farmer's best strategy to maximize the production of white babbits?

Solution Preview

This question is just analyzing one gene. It is not sex linked so we don't treat it any differently. Babbits that have a B will be black. In order to be white, they must be bb.

To start this question, we must determine the genotypes of the parents. They are both black so they must have a B. They also produce white babbits, so therefore they must also BOTH have a b. Therefore the parental cross is Bb x Bb.

The offspring of this cross will be ...