/sci/ - Science & Math

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Help !!3HTTeV/IWxA Sun Jun 6 19:59:09 2010 No.1123510 [Reply] [Original]

Hey guys. I'm having trouble revising for my genetics exam. I'd really appreciate it if somebody could help me.

I'm looking over past exam questions. Here's one that is giving me a lot of trouble:

Body colour is controlled by variation at a single locus in a blowfly species. The D allele confers dark body and the d allele light body. A population cage was initiated with the D and d alleles at equal frequency. The relative fitness of the three genotypes have been measured in the cage and shown to be D/D 1.00, D/d 0.95, d/d 0.90.

(a) Given these relative fitness values for the three genotypes, what will be the expected frequency of the D allele after TWO generations of selection?
(b) What is the expected equilibrium frequency of the D allele?
_____________________

For (a), we know that p = 0.5 and q = 0.5, but we're asked for the frequency of D after 2 generations. We also know the fitness values. To find the frequency after 1 generation, can you just sub in the known values into the formula in the picture? That would give you the expected frequency after the first generation, right? Then we can just use the new values and use the same formula again to get the expected frequency after the second generation?

Also, with the formula, I can see that it's "q1" that we're looking for but, since p and q are at equal frequencies in the beginning, can we just treat "q1" as "p1"?

Sorry if it was a bit longwinded...

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