Two Questions: Dan's Lecture 3, Slide 38 (last slide of Lecture 3)
Dan
Slide 38 of lecture 3 describes allelic % of 'q' that is in hets vs
homozygotes.
I see 'q' within 'q hets' as = (0.5) x 2pq and 'q' within 'q
homozygotes = q^2.
That being said, would not the problem be set up as % 'q' in 'q
homozygotes' =
((0.5) x 2pq / q^2) x 100 = %
Perhaps I am missing the main take-away message you were trying to
convey on this slide. If so, please straighten me out. Thanks
Prof Dan
The point here is that according to Hardy-Weinberg Equilibrium, rare
alleles are mostly in heterozygotes compared to homozygotes of that
rare allele. HWEq says hets will be at a frequency of 2pq and if our
rare allele is q then homozygotes will be at a frequency of q^2
(that's q squared). We can use the genotype frequencies to calculate
the ratio of alleles in heterozygotes vs homozygotes. That would be
just 2pq : q^2, except that heterozygotes only have one rare allele
and homozygotes have two. So its 2pq : 2q^2. Because its a ratio you
could write it pq : q^2. It doesn't really matter.
Does that help?
Dan