Caenorhabditis elegans (the famous model organism used in biomedical research fo

Question

Caenorhabditis elegans (the famous model organism used in biomedical research for which 3 Nobel prizes have been awarded) has 5 autosomes and an X chromosome. Hermaphrodites have two X chromosomes (XX) and males have only one (that is, males are XO, where the "O" stands for "no homolog for the X", or "nullo"). What is the total number of possible combinations of chromosomes in C. elegans male sperm due to independent assortment at Metaphase l of meiosis? [Another way to think about the question is, disregarding recombination/crossing-over what is the total number of genetically different male gametes produced, assuming that homologous pairs are different in at least one locus?] Explain your answer.

Explanation / Answer

There is the following four types of male gametes would form:

AAA +X, AA+X, AAA+0, AA+0

This is because C. elegans has 5 autosomes which will divide in frame of AAA and AA. Now males has one X chromosome so it will taken by two cells having AAA and AA to form AAA +X, AA+X; which are required for female production. And other gametes will no sex chromosome and have combination of AAA+0, AA+0; this is required for male production.

If 1 allele locus difference in homologous pair then the following genetically different gametes will occur

The four chromosome gamete AAA +X has possibility of combination 4! = 4x3x2x1 = 24

The three chromosome gametes AA+X and AAA+0 have possibility of combination (3! For each) x2 = (3x2x1) x 2 = 12

The two chromosome gamete AA+0 has possibility of combination 2! = 2x1 = 2

So total genetically different gametes will occur = 24+12+2 = 38

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---