Question

1. If AaBbCcDd is mated to AaBbCcDd (no gene interactions among all genes), what is the probability that the offspring will have either the phenotype AaB_CcDD or the genotype AAbbCcD_? (assuming complete dominance for genes) (Show procedure, NO score for direct result)

2. A mouse sperm of genotype a BCDE fertilizes an egg of genotype a bcDe. What are all the possibilities for the genotypes of (a) the zygote and (b) a sperm or egg of the baby mouse that develops from this fertilization? (Show procedure, NO score for direct result)

3. What probability of offspring from cross (AaBbCc x AabbCc) is predicted to show the recessive phenotypes for at least two of the three traits? (assuming complete dominance for genes) (use either branched-line or Punnett square to explain; NO score for giving the direct probability)

4. If the a and b loci are 30 cM apart and an AA BB individual and an aa bb individual mate: What gametes will the F1 individuals produce, and in what proportions? What phenotypic classes in what proportions are expected in the F2 generation (assuming complete dominance for both genes) (show procedure, NO score for direct result)?

5. AABB and aabb individuals were crossed to each other, and the F1 generation was backcrossed to the aabb parent. 995 AaBb, 997 aabb, 3 Aabb, and 5 aaBb offspring resulted.

1. How far apart are the a and b loci?
2. What progeny and in what frequencies would you expect to result from testcrossing the F1 generation from a AAbb X aaBB crosss to aabb?
3. In a typical meiosis, how many crossovers occur between genes A and B?
4. Assume that the A and B loci are on the same chromosome, but the offspring from the testcross described above were 496 AaBb, 504 aabb, 502Aabb, and 498 aaBb. How would your answer to part (c) change.

Answer 1

We have entitled to answer only one question. So i will answer the second one (mouse problem).

Mouse sperm Mouse egg BCDE X bcDe F1 progeny -----> BbCcDDEe (Baby mouse)

a) The genotype of the Zygote is ------> BbCcDDEe

b) Now come to the genotype of sperm or egg of this baby mouse. First of all we have to know that the all cells of this baby mouse contain same genotype including germ cell also. So the genotype og germ cells are BbCcDDEe. It contain 3 different type of gene, according to formula number of gametes produced = 2n

Where n = Different number of genes = 3 , No. of gametes produced by germs cell = 23 = 8

That means the sperm or egg contain 8 different type of genotype. The possible genotypes are given below,

1) BCDE 2) bcDe 3) BcDE 4) BCDe 5) bCDE 6) bcDE 7) bCDe 8) BcDe