biology help please!!!?

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Maria R

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in a population of minnows, body colors is controlled by a single locus with two alleles showing incomplete dominance. homozygotes for one allele (A1) are red, homozygotes for the other alleles (A2) are yellow, and heterozygotes are orange. Sunfish prefer red minnows over yellow ones and yellow minnows over orange ones, As a results, relative to orange minnows, survivorship to maturity is 50% less in red minnows and 20% less in yellow minnows. Initial genotype frequencies in a group of newborn offspring (before predation had acted) were A1A1=0.150 A1A2=0.350 and A2A2= 0.5

how would i go about calculating the expected genotype frequencies in the offspring that survive sinfish redation and reach maturity? Also, how would i calculate the initial genotype frequencies of THEIR newborn offspring?

please help! i know its a long question but im really stuck. I would like to know how to do it...not just the answers. thanks! :D
 
That's a weird question.

so you have to assume that orange ones survive 100% (this is all relative, so you can make that assumption), yellow ones survive 80%, red ones survive 50%.

Next, we may have to assume that the genotype frequencies remain the same with each generation (if they aren't hunted by sunfish). This may be a fair assumption because they appear to be in Hardy-weinburg equilibrium.
Lets also assume there are a total of 100 minnows (doesn't matter what the number is because we are working with fractions).

If there are 100 minnows, the following are the frequencies:
A1A1 = 100*0.150 = 15
A1A2 = 100* 0.350 = 35
A2A2 = 100 * 0.5 = 50

After predation, lets assume A1A2 all live to maturity:
[A1A2] = 35
[A1A1] = 0.5 * 35 = 17.5 (50% survive)
[A2A2] = 0.8*50 = 40

Calculate new genotypic frequencies (Now there are a total of 92.5 minnows):
[A1A2] = 35/92.5 = 0.378
[A1A1] = 17.5/92.5 = 0.189
[A2A2] = 40/92.5 = 0.432

That would be my answer.

PS: I wouldn't have answered the question if you didn't ask for a good explanation about how to do it. It really looked like you were interested in the method rather than the answer.
Good luck!
 
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