# destroyer 144

Discussion in 'DAT Discussions' started by pistolpete007, Jun 15, 2008.

1. ### pistolpete007

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if 36% of a population ahs blue eyes, what is the percentage of the recessive allele?

why isnt the answer just 36% they are asking for the percentage of the recessive allele ....blue eyes are recessive allele so isnt the 36% the percentage of recessive allele?

3. ### TexasDent

You can simply say q=the percent of recessive alleles(b) and q^2=the percent of recessive homozygotes (blue eyes or bb)
so: q^2=.36 and the sq. root of .36 = .6=q (the percent of recessive alles) or 60% recessive alleles

You could also use the hardy weinberg equations to check and make sure that this adds up:
Since the question tells us that 36% of the pop. has blue eyes(bb which is q^2) then we know that q^2=.36 , so q=.6
Then use p+q=1 to get p+.6=1 and p=.4
Now we will use the equation: p^2 + 2pq + q^2 = 1 ; to find the percent of the population that is heterozygous and divide this numer by 2 to find the percent of blue alleles in the heterozygotes and add this to q^2 (the percent of blue alleles in the recessive blue eyed pop.)

Since the amount of blue alleles in a heterozygote is half the percent of heterozygotes we do: (2pq)/2........(2*.4*.6)/2=.24(b alleles in the heterozygotes)
.24+.36=.60 or 60% recessive allele

Hope this explanation clears everything up...

4. ### osimsDDS

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let me put this in an easy way to understand...when they say 36% of the population has blue eyes they are talking about the frequency of the recessive phenotype...a phenotype is made from 2 allels, either an A or a, can be homozygous dominant, recessive, or heterozygous...so when they say frequency they are talking about 2 alleles...

Now they want to know what is the frequency of the recessive ALLELE...that means they just want to know 1 allele, the a allele not aa or AA or Aa...

So you have to take the square root...

Think of it like this 36% = aa
But they want to know just a (1 allele), so a will equal .6 or 60%

5. ### pistolpete007

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that makes so much more sense thanks a lot

so pretty much q=a and p=A and q^2=aa and p^2=AA right?

6. ### osimsDDS

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yea and 2pq=Aa

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