Chromosome #4, an autosome of the diploid smorglefuger, is rod-shaped and normal

Question

Chromosome #4, an autosome of the diploid smorglefuger, is rod-shaped and normally has its centromere positioned at one end (telocentric). A circular variant of this chromosome exists, and except for the lack of physical ends (telomeres) of the chromosome, it is identical in genetic content to the rod-shaped variety; therefore, the two variants will synapse normally. The position of five genes (a-e) on the two forms of this chromosome are shown below; the five genes are all equally spaced along the chromosome.

Here are three different females of the genotype a+b+c+d+e+/a b c d e. The structures of their homologous pair of chromosome #4 are indicated. Each of these types of female is testcrossed to homozygous a b c d e males that carry chromosome #4 only as its normal rod form.

1. Everything else being equal, which, if any, female type(s) will produce the highest fraction of phenotypically a+b+c+d e progeny?

Select all that apply.

2.Everything else being equal, which, if any, female type(s) will produce the highest fraction of phenotypically a b c d+e individuals?

Select all that apply.

please explain, Thanks

female A female B female C none will produce those progeny a bcd e normal rod form circular form centromere

Explanation / Answer

1) Female A

2) Female A

Explanation: Explainantion of both is same that to acheive a+b+c+d e and a b c d+e progeny chromosomes has to undergo single crossing over. But single crossing over is vary rare phenomenon in circular chromosome. So only rod chromosomes can show possibility of single crossing over.

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