When chromosomes are examined cytologically, it is often possible to determine i

Question

When chromosomes are examined cytologically, it is often possible to determine if the homologs are paired or unpaired. Paired homologs are called bivalents, while unpaired homologs are called univalents. Caenorhabditis elegans has six pairs of chromosomes. Mutants in the gene him-5 in C.elegans affect some process in pairing and synapsis in prophase l, but precisely what process is affected is not clear. Different oocytes from a him-5 mutant hermaphrodite can have different karyotypes. How can the following karyotypes at the end of prophase l be explained? a. Six bivalents and no univalents b. Twelve univalents and no bivalents c. Five bivalents and two univalents d. Three bivalents and six univalents 6.12

Explanation / Answer

c. FIVE BIVALENTS and TWO UNIVALENTS as mutation in him-5 gene affects x chromosome more rather than autosome so as hermophrodite have xx chromosome and c.elegans have total 6 pair of chromosome in which one pair detrmine its sex i.e xx(hermophrodite) in this case so only xx chromose affected by him 5 gene mutation and became univalent while all 5 autosome pair remain in bivalent form.

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