HardyWeinberg Model

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Topic 5

• Hardy-Weinberg Model

mathematician
physician
"Now, in the first place, I deny that the
mathematical theory of population genetics is at
all impressive, at least to a mathematician."
J. B. S. Haldane
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Chromosomes
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(No Transcript)
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Example
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Human Blood Groups (European Americans)
alleles M (p) N (q) genotypes MM MN NN nu
mbers of genotypes 1787 3039 1303 total
population size 1787 3039 1303
6129 genotype frequencies f(MM) MM/Total
1787/6129 0.2915 f(MN) MN/Total
3039/6129 0.4958 --gt 1 f(NN)
NN/Total 1303/6129 0.2125
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Parental Allele Frequency
frequency of M allele (MM 1/2 MN)/Total
(1787 3039/2)/6129 3306/6129 53.9 (.539)
frequency of N allele (NN 1/2 MN)/Total
(1303 3039/2)/6129 2822/6129 46 (.460)
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Expected Genotype Frequency
Frequency of MM (p2) (0.539)2 .2905
Original Genotype frequency MM 1787/6128 .2916
These are virtually identical. Conclude MN gene
is in HW equilibrium.
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Calculation of Allele Frequency (M)
alternative methods
1. Using genotype frequencies 0.2915
1/2(0.4958) 0.539
2. Using numbers of genotypes (1787 x 2)
3039 /(6129 x 2) (3574 3039)/12258 0.539
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An application of HW Phenylketonuria

• Normal child Phenylalanine ----gt Tyrosine
• Recessive disease, chromosome 12
• defective enzyme phenylalanine hydroxylase
• Phenylalanine --//--gt Tyrosine
• 1/10,000 babies afflicted in USA
• Calculate fraction that are carriers.

HOMEWORK
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Genotype Frequency Before Selection
Genotype Frequency After Selection
Relative Fitness
After Selection
Genotype AA Aa aa
Phenotype 250 500 250
Survival 100 90 80

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Genetics Vocabulary