Ap Bio help-- question on evolution- equilibrium

Test Preparation AP Test Preparation
1

<p>Can anyone remind me how to answer this question?
It would be very helpful if someone could answer it and show the steps taken:</p>

<p>--- Calculate the frequency of alleles and the frequencies of genotypes in the following population, where brown is recessive and yellow is dominant:
5,000 brown dogs and 15,000 yellow dogs.</p>

<p>Thank you very much and please answer as promptly as possible.</p>

2

<p>1:2:1 (cross of two heterozygotes)</p>

3

<p>you are supposed to use an equation for this (p+1)^2...</p>

4

<p>You will use these equations:</p>

<p>p+q = 1
p^2 + 2pq + q^2 = 1</p>

<p>p = how many dominant alleles there are
q = how many recessive alleles there are</p>

<p>p^2 = frequency of homozygous dominant
2pq = frequency of heterozygous organisms
q^2 = frequency of homozygous recessive</p>

<p>so:</p>

<p>25% of population has brown recessive allele
75% of population hass yellow dominant allele</p>

<p>6.25% is homozygous brown
37.5% is heterozygous
56.25% is homozygous yellow</p>

5

<p>Thank you very much for the help!!!!!!!!!!!!!!!</p>

6

<p>The equation models the Hardy-Weinburg Equilibrium, just in case you were wondering.</p>

7

<p>


Given only this information, the problem cannot be solved. We need to be told whether or not the population is in Hardy-Weinberg equilibrium

this is obviously incorect, since we already know that 25% of the population brown (5,000 out of 20,000), so how can 6.25% also be correct for homozygous brown?</p>

<p>Assuming the population is in equilibrium, q^2 would be .25, so q would be .5, therefore p is also .5</p>

<p>So,
q^2 = Homozygous brown - 25%
2pq = Heterozygous yellow - 50%
p^2 = Homozygous yellow - 25%</p>

<p>Moral of this story:
Always make sure your calculated numbers have some relationship to your real data</p>

8

<p>frasi, be careful not to confuse allele frequencies with genotype frequencies; they are quite different. That is where Boridi went wrong...the 1/4 of the dog population that is brown corresponds to p^2, not p.</p>

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<p>sorry
10char</p>