1 / 13

Variety of mating systems

Variety of mating systems. Panmixia Assortative mating Disassortative mating Outcrossing Inbreeding Mixed mating. Disassortative mating. What is the equilibrium frequency of alleles S1, S2, S3, and S4? What is the fate of a new mutation that produces allele S5?. Inbreeding.

ami
Download Presentation

Variety of mating systems

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. Variety of mating systems • Panmixia • Assortative mating • Disassortative mating • Outcrossing • Inbreeding • Mixed mating

  2. Disassortative mating What is the equilibrium frequency of alleles S1, S2, S3, and S4? What is the fate of a new mutation that produces allele S5?

  3. Inbreeding What is inbreeding? Forms of inbreeding

  4. Genetic consequences of inbreeding Loss of heterozygosity Do allele frequencies change (i.e., does inbreeding result in evolution)?

  5. Genetic consequences of inbreeding Heterozygosity: Homozygosity: Genetic variance within lines: Genetic variance among lines: Response to selection among lines: Fitness of inbred lines:

  6. The inbreeding coefficient, Wright’s F Sewall Wright 1889-1988

  7. The inbreeding coefficient, Wright’s F F ranges from 0-1 • 0 = completely outbred (H-W) • 1 = completely inbred (homozygous) F can be thought of as: • Proportional loss of heterozygosity • Probability of homozygosity • Half the coefficient of relatedness of the parents F is measured relative to some starting population, which is usually assumed to have F = 0

  8. The inbreeding coefficient, Wright’s F From Hartl and Clark Fig. 4.15

  9. Genotype frequencies as a function of F AA: p2 + pqF Aa: 2pq - 2pqF aa: q2 + pqF

  10. How can F be estimated if we don’t have a pedigree for the whole population? HI = observed heterozygosity at neutral loci (usually with molecular markers) HT = heterozygosity expected under H-W (2pq) Aa: 2pq - 2pqF = HI 2pq(1-F) = HI HT(1-F) = HI F = 1-(HI/HT) F = (HT-HI)/HT

  11. Inbreeding depression What is inbreeding depression? What causes inbreeding depression? How do organisms avoid inbreeding depression?

  12. Inbreeding Scientists find no biological reason to stop first cousins from marrying • Risks to children born to cousins not as high as previously thought By Denise Grady The New York Times Thursday, April 4, 2002 Sarah Wedgwood Josiah Wedgwood I Robert Darwin Susannah Wedgwood Josiah Wedgwood II Mrs. JWII Charles Darwin Emma Wedgwood

  13. Is inbreeding always bad? By exposing recessive alleles to selection in homozygotes: • Leads to rapid fixation of beneficial recessive alleles • Purges deleterious recessives; aka, lightens the genetic load

More Related