d. Draw the arrangement of alleles on the chromosomes of the heterozygous parent
ID: 196051 • Letter: D
Question
d. Draw the arrangement of alleles on the chromosomes of the heterozygous parent? (2 points) 2. In Drosophila, the genes b (black body), vg (vestigial wings), and c (curved wings) are linked. The genes are in the order vg-b-c. Shown here is the genotypic arrangement in a heterozygous fly: a. Indicate all of the different gamete genotypes that could arise from this parent. b. What two gamete genotypes will be made in the highest frequency from this heterozygote? c. What two gamete genotypes will be made in the lowest frequency from this heterozygote? (2 points)Explanation / Answer
ANSWER 2.
Genes b (black body), vg (vestigial wings), and c (curved wings) are linked.
Genes are in the order vg-b-c.
Genotypic arrangement in a heterozygous fly =
vg- b+ c+
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vg+ b- c-
Answer a.
Apart from the Mendelian law of segregation, we have to take into account crossing over, which might lead to exchange of genetic material, as such, all of the different gamete genotypes that could arise from this parent:
vg- b+ c+ , vg+ b- c- , vg- b+ c- , vg+ b- c+ , vg+ b+ c+ , vg- b- c- , vg+ b+ c- & vg- b- c+
Answer b.
Since the frequency of recombination is lesser, hence the chances of crossing over not splitting the original configuration is higher, as such, the two gamete genotypes that will be made in the highest frequency from this heterozygote:
vg- b+ c+ &vg+ b- c-
Answer c.
Since the frequency of recombination is lesser, hence the chances of crossing over occurring twice is the largest which will result in two chiasmas in between 3 genes, as such, the two gamete genotypes that will be made in the lowest frequency from this heterozygote:
vg+ b+ c- & vg- b- c+
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