Chromosome #4, an autosome of the diploid smorglefuger, is rod-shaped and normal
ID: 67353 • Letter: C
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.
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.
female A
female B
female C
none will produce those progeny
Everything else being equal, which, if any, female type(s) will produce the highest fraction of phenotypically a b c d+e individuals?
female A
female B
female C
none will produce those progeny
Explanation / Answer
Female A-
abcde/abcde
Female B-
abcde/a+b+c+d+e+
Female C-
a+b+c+d+e+/a+b+c+d+e+
Hence, highest fraction of phenotypically a+b+c+d e progeny will be produced through a test cross between C and homozygous a b c d e males
Hence, highest fraction of phenotypically a b c d+e individuals will be produced through a test cross between B and homozygous a b c d e males