BIO_1B HARDY-W - ByRuthKirkpatrick ForTwoAlleles...

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A Guide to Solving Almost Any Hardy-Weinberg Genetics Problem By Ruth Kirkpatrick For Two Alleles Step 1: First write down these two equations. They are always true. p + q = 1 where p = frequency of allele A, q = freq. of allele B AA + AB + BB = 1 where AA = freq. homozygous dominant genotype AB = freq. heterozygous genotype BB = freq. homozygous recessive genotype Step 2: Does the problem allow you to assume that the alleles are in Hardy -Weinberg equilibrium? If so, you can write down this third equation: P 2 + 2 pq + q 2 where p 2 = frequency of AA 2pq = frequency of AB q 2 = frequency of BB If you aren't given this as an assumption, the problem often will be asking you to figure out if the alleles are in fact, in equilibrium. Step 3: What information are you given about allele or genotype frequencies? It is often possible to figure out all the other alleles and genotype frequencies by the process of deduction, and you can do this before directly attacking the question at hand. -Are you given the frequency of an allele p? Find q = 1-p. Next, if you can assume H- W, you can figure out the genotype frequencies using equation 3: p 2 = AA, 2pq = AB, q 2 = BB. -Are you given either of the homozygous genotypes AA or BB? If you can assume H-W, take the square root of the frequency using p 2 = AA or q 2 = BB and then deduce the allele frequencies. If you are just given the heterozygote frequency, then this is one situation where you cannot deduce the allele frequency when provided with only this information.
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