A woman is heterozygous for three linked autosomal genes: GgHhMm. Her husband is

Question

A woman is heterozygous for three linked autosomal genes: GgHhMm. Her husband is homozygous recessive for each of the genes. They have eight children with the following genotypes:

Three are GghhMm.

Two are ggHhmm.

One is GgHhmm.

One is Gghhmm.

One is gghhmm.

a. What is the most likely combination of alleles on each of the mother’s chromosomes? Explain.

b. List the genotypes of the recombinant children above. For each of these children, determine the location of the required crossover(s) in the mother’s oocyte to create their recombinant chromosome by identifying the two genes between which the crossover(s) occurred.

c. List the other possible recombinant genotypes that have not appeared in the offspring.

ONLY ANSWER IF YOU SPECIALIZE IN GENETICS PLEASE.

Explanation / Answer

Answer:

a).

Mother genotype: GHM / ghm

Father genotype: ghm / ghm

Mother produces 8 types of gametes by crossing over in different ways.

If single crossing over between G & H, it yields Ghm & gHM gametes.

If single crossing over between H & M, it yields GHm & ghM gametes.

If double cross over between G & H and H&M, it yields GhM & gHm gametes.

If cross over does not happened, it yields GHM & ghm gametes.

b).

GghhMm = Double cross over happened between G & H and H&M in oocytes.

ggHhmm = Double cross over happened between G & H and H&M in oocytes.

GgHhmm = Single cross over happened between H & M, in oocytes.

Gghhmm = Single cross over happened between G & H, in oocytes.

gghhmm = No cross over in oocytes

c).

The following recombinant genotypes have not appeared.

gghhMm (from single cross over between H & M, in oocytes)

ggHhMm (from single cross over happened between G & H, in oocytes)

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