Random Intro to Genetics Question

[amy123]

If an individual has 10 gene pairs, how many different types of gametes can be formed if five of the gene pairs are homozygous and the remaining 5 gene pairs are heterozygous?

 

42

109

32

1024

None of the above....

 

Thanks!

[DctrZaius]

It depends if and where homologous recombination occurs. It's unlikely that genes close to the centromere will recombine. If we assume that all of the alleles can re-assort then the statistics would be something like 10x9x8x7x6x5x4x3x2x1 = 3,628,800 different possible combinations of alleles in one gamete. Makes you feel unique, huh?! (Also, I was assuming that all 10 genes are on one chromosome. You would need to add even more statistics to accommodate for the number of chromosomes within an organism. If there are 10 chromosomes in an organism, with 10 genes on each, then the hypothetical possible number of gametes would be 3,628,800^2)

Edited October 13, 2010 by DctrZaius

[Mr Skeptic]

The simplified version is that you choose one of your two alleles for each gene. You should be able to figure this out, so at least take a guess. I'll ask some questions to help:

For the homozygous genes, how many choices of allele are there?

For the heterozygous genes, how many choices of allele are there?

Note that the choice of one gene is not independent of the others due to the way recombination works, but that will just change the odds of any particular combination, not the number of possible combinations.