What single cross does she perform? What will be the result of this cross for ea

Question

What single cross does she perform? What will be the result of this cross for each of her the possible outcomes (sable, black, and ebony)?

Fall 2018 c. Despite the fact that some of the kittens have tails, the Manx tailless phenotype is considered to be penetrant. Do you agree with this assessment, or would you think that this tailless phenotype has reduced penetrance? Assuming that you had the space and patience to breed many cats, how could you determine if the tailless phenotype is, in fact, highly penetrant? (3 pts) 4. When one of the stock vials in the fly room got damp, the piece of laboratory tape with the label for the Drosophila stock fell off, so the research student could not tell the genotype of the flies in her vial. She could see that the flies in her unlabeled vial-both males and females-had a black body, among other phenotypes, so if she can determine which gene is giving rise to this black body color, she can infer the rest of the genotype of her stock. She also knew that she had been working with stocks that had each of three different recessive mutations that gave rise to a black body similar to her unlabeled flies: the X-linked gene sable, a gene on chromosome 2 known as black, and a gene on chromosome 3 known as ebony. She had separate vials with homozygous sable, black and ebony flies to work with a. How could she determine the genotype of the flies in her unlabeled vial? Explain what crosses she could make and what the results would be for each cross. (3 pts) b. The research student is very clever and figured out that she could get the same information as in (a), but with only a single cross. What single cross does she perform? What will be the result of this cross for each of her three possible outcomes (sable, black and ebony)? (4 pts) 5. Two agouti mice are crossed, and over a period of a year they produce 48 offspring with the following phenotypes: 28 agouti mice 7 black mice

Explanation / Answer

Single-Gene Test Crosses:

Recall that in the fruit fly Drosophila melanogaster, the ebony-body allele (e) is recessive to the normal yellow-body allele (E). Say you are given a male fly with a yellow body.

In order to set up your test cross, you must first realize that the male fly has one of two possible genotypes: Ee or EE. Because the male exhibits the dominant body color phenotype, you must cross it with a female with the homozygous recessive phenotype and genotype. Thus, the male fly is crossed with an ebony-bodied female of genotype ee. Depending on the male fly's underlying genotype, this cross will yield one of two possible sets of outcomes.

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