1 / 11

Hardy Weinberg Theorem and Equilibrium

Hardy Weinberg Theorem and Equilibrium. IB Topic/Option D4 Campbell Text pages 447-449. HW theorem describes a non-evolving population. 1908

maida
Télécharger la présentation

Hardy Weinberg Theorem and Equilibrium

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Hardy Weinberg Theorem and Equilibrium IB Topic/Option D4 Campbell Text pages 447-449

  2. HW theorem describes a non-evolving population • 1908 • The frequency of alleles and genotypes in a population remain constant over generations unless acted upon by agents other than Mendelian segregation and recombination of alleles • Meiosis and random fertilization has no effect on the overall gene pool of a population

  3. The Hardy Weinberg Equation • If a population is in genetic equilibrium, predictions can be made about genotypic, phenotypic, and allele frequencies • The equation can be used for more than 2 alleles, but we’ll keep it simple

  4. HW Equation • p2 + 2pq + q2 = 1 • p + q = 1 • the sum of both frequencies equals 1 (100%) • p = frequency of dominant allele • The probability of being homozygous dominant (RR) is p x p • q = frequency of recessive allele • The probability of being homozygous recessive (rr) is q x q • 2pq • The probability of having heterozygous genotype • Frequency of Rr plus rR • The dominant and recessive allele can come from either parent

  5. PRACTICE! • In a population with two alleles for a particular locus, B and b, the allele frequency of B is 0.7. What would be the frequency of heterozygotes if the population were in Hardy Weinberg equilibrium? • 0.42

  6. More Practice! • In a population in HW equilibrium, 16% of the individuals show the recessive trait. What is the frequency of the dominant allele in the population? • 0.6

  7. Do people actually use this equation? • Yes! • Population genetics and health science • Can be used to estimate the percentage of the human population that carries the allele for a particular inherited disease • PKU (See page 449)

  8. HW Theorem and Genetic Variation • Important conceptually and historically • Shows how Mendel’s theory of inheritance “plugs a hole” in Darwin’s theory of natural selection • Natural selection requires genetic variation • HW theorem explains how Mendelian inheritance preserves genetic variation from one generation to the next • Remember Punnett squares? (See page 448)

  9. Assumptions of the HW Theorem • In order for a population to be in HW equilibrium, 5 conditions must be met: • 1. Very large population • 2. No migration • 3. No net mutations • 4. Random mating • 5. No natural selection

  10. Therefore, … • We do not really expect a natural population to be in Hardy Weinberg equilibrium • Deviation from a stable gene pool and HW equilibrium usually results in evolution

  11. Animations and tutorial • http://science.nhmccd.edu/BioL/hwe.html

More Related