## Population Genetics (Hardy Weinberg) problem

**Moderator:** BioTeam

### Population Genetics (Hardy Weinberg) problem

Hello, this is my first post.

I am having trouble with a homework problem that should be really easy, and I can't figure out what I'm doing wrong.

Here it is:

In eggplants, fruit color is determined by a gene with two alleles: an allele that codes for purple fruit (Z) and an allele that codes for white fruit (W). Heterozygotes have neither purpler nor white fruit; instead ,their fruit is an intermediate color, light violet. A population of 10,000 eggplants is in Hardy-Weinberg equilibrium. In this population, the frequency of individuals with a genotype homozygous for the white allele is .49.

Here is what I did:

Calculate the Allelic frequencies:

p= the frequency of the allele Z = .3 (1-q)

q= the frequency of the allele W = (square root of .49) =.7

Calculate the genotypic frequencies:

genotype ZZ = p^2=.09

genotype WW = q^2 = .49

genotype ZW = 2pq = .0882

This should all add up to 1, but it doesn't and I can't figure out what I'm doing wrong.

I'm sure I'm missing something so basic that I'm going to be embarrassed for even posting this problem. Regardless, any help is much appreciated.

I am having trouble with a homework problem that should be really easy, and I can't figure out what I'm doing wrong.

Here it is:

In eggplants, fruit color is determined by a gene with two alleles: an allele that codes for purple fruit (Z) and an allele that codes for white fruit (W). Heterozygotes have neither purpler nor white fruit; instead ,their fruit is an intermediate color, light violet. A population of 10,000 eggplants is in Hardy-Weinberg equilibrium. In this population, the frequency of individuals with a genotype homozygous for the white allele is .49.

Here is what I did:

Calculate the Allelic frequencies:

p= the frequency of the allele Z = .3 (1-q)

q= the frequency of the allele W = (square root of .49) =.7

Calculate the genotypic frequencies:

genotype ZZ = p^2=.09

genotype WW = q^2 = .49

genotype ZW = 2pq = .0882

This should all add up to 1, but it doesn't and I can't figure out what I'm doing wrong.

I'm sure I'm missing something so basic that I'm going to be embarrassed for even posting this problem. Regardless, any help is much appreciated.

### Re:

JackBean wrote:for me 2*0.3*0.7 = 0.42 not 0.0882

and that makes up 1 exactly

That would be fine, except that it's not 2*0.3*0.7

Its p^2+q^2+2pq

.03^2+.07^2+2[(.03^2)*(.07^2)]

...which does not equal 1.

Am I making this more complicated than I have to?

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