Discussion Assignment #4

Hide and Seek

Okay, easier questions this week, but you're still going to have to put your thinking caps on and work a bit.

In gerbils, the wild type brown fur color is dominant to black fur color. This color variation is controlled by a completely different gene than the copper color variant discussed last week. This brown/black gene is autosomal.

You've got ten brown female gerbils. How can you determine which of them are homozygous brown, and which are heterozygous for these two alleles?

Again in gerbils, yet another gene is responsible for a coloration called "albino." The normal product of this gene is one of the enzymes (catalysts) that enables one of the steps in the production of the pigmentation< in fur and eyes. If the gerbil doesn't have this enzyme, it can't produce that pigment, and its fur will be white, its eyes red./P>

The normal allele of this gene is completely dominant to the albino allele.

You mate two gerbils. Each of these gerbils is heterozygous for the brown/black gene from question one, and each is also heterozygous for the albino gene. So your mating is:

BbAa X BbAa

What color are these two gerbils? Complete the mating problem. What phenotypic ratio do you predict you will get? Remind yourself of the meaning of "phenotype" before you answer this question.

Consider the following two matings. Each of them involves two genes; all of the genes in question are autosomal, and in all cases the allele represented byt the capital letter is completely dominant to the allele represented by the lower case letter. Though these are rather... unusual creatures, their geneic systems work exactly like ours.

First, in Venusian Mugwords, there are two common antenna lengths. Some mugworts have antennae that are aboutr 15 cm long; others have antennae that are about 5 cm long. Long antennae (L) is completely dominant to short antennae (l). There are also two common body colors among the fashion conscious mugworts. Safron yellow body (B) is completely dominant to cobalt blue body (b).

Your mating is:

LlBb X llbb

The result among the offspring of this mating:

Your second mating utilizes Martian Torwhols. These creatures have either six or eight legs. Six legs (S) is completely dominant to eight legs (s). Their bodies have either sharp corners (C) or rounded corners (c). Sharp is completely dominant to round.

Again, your mating is:

SsCc X sscc

And the offspring:

Before you look at the offspring, these two matings look like they should be exactly the same. Remember, the genetics of these two creatures work just the same as those of humans. None of the genes is sex linked.

What explanation can you come up with for these two different results? Hint: The answer to this is connected to things that go on in meiosis.

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