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Lecture 9

Lecture 9. Hardy–Weinberg equilibrium. Wilhelm Weinberg (1862-1937). Godfrey Hardy (1877-1947).

debra-sutton
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Lecture 9

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  1. Lecture 9 Hardy–Weinberg equilibrium Wilhelm Weinberg(1862-1937) Godfrey Hardy(1877-1947)

  2. The Hardy–Weinberg principle (also known as the Hardy–Weinberg equilibrium, model, theorem, or law) states that allelic and genotypic frequencies remain constant in the absence of evolutionary influences. These influences include non-random mating, mutation, selection, genetic drift, gene flow and meiotic drive http://www.youtube.com/watch?v=JsuJlewaPX0

  3. Hardy-Weinberg equilibrium equation • p² + 2pq + q² = 1 • p = AA + ½Aa • q = aa + ½Aa • p + q = 1 p = 1 – q THIS means!!! • p² + 2pq + q² = 1 • p²is the predicted frequency of homozygous dominant (AA) • 2pqis the predicted frequency of heterozygous (Aa) • q²is the predicted frequency of homozygous recessive (aa)

  4. Significance of the Hardy-Weinberg Equation • 20th century, geneticists were able to use Punnett squares to predict the probability of offspring genotypes • Mendelian rules of dominance and recessiveness • Hardy-Weinberg equation essentially allowed geneticists to do the same thing for entire populations

  5. Albinism • Albinism is a rare genetically inherited trait that is only expressed in the phenotype of homozygous recessive individuals (aa). The most characteristic symptom is a marked deficiency in the skin and hair pigment melanin. This condition can occur among any human group as well as among other animal species. The average human frequency of albinism in Africa is only about 1 in 20,000. The frequency of homozygous recessive individuals (aa) in a population is q². Therefore: q² = 1/20,000 = 0.00005 and q = 0.007 Use p + q = 1 and p² + 2pq + q² = 1 and calculate the predicted Genotypes in the population

  6. Humans inherit either the M or the N antigen which is determined by two different alleles at the same gene locus. If we let the frequency of allele M=p and the frequency of the other allele N=q, then the next generation's genotypes will occur as follows: Frequency of MM genotype = p2 Frequency of MN genotype = 2pq Frequency of NN genotype = q2 We can take a sample of the population and count the number of people with each genotype. For example, a sample of 5000 from Forensic Town, USA, has 990 of type NN, that is 990/5000 or 19.8%

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