Inbreeding - uncle niece, first cousins) there is a chance...

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Inbreeding When random mating occurs and no forces are acting to alter gene frequencies we expect genotype frequencies to be distributed in the ratio p 2 (AA) + 2pq (Aa) + q 2 (aa) What happens if matings do not occur at random? By looking at self-fertilization, the most extreme form of inbreeding possible, we can predict the effects. In the chart below, a Pink (heterozygous) 4-o'clock is selfed and the progeny allowed to self pollinate over 3 more generations. In each generation: • half the heterozygosity is lost • the frequency of homozygous individuals increases • the gene frequencies remain constant The same effects occur but at a slower rate if less extreme systems of mating are used. In consanguineous matings (matings between relatives such as brother-sister,
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Unformatted text preview: uncle niece, first cousins) there is a chance that the same defective allele was inherited from a common ancestor. This means that for such a gene, the chance of having an affected child is much greater than if the partner was a non-relative. The realization that R'R Genotypes % Heterozygous f(R') f(R) 100 0.5 0.5 Generation 1 2 1R'R' 2R'R 1RR 50 0.5 0.5 (selfing, assuming 4 progeny per plant in a perfect ratio) 3 6R'R' 4R'R 6RR 25 0.5 0.5 4 28R'R' 8R'R 28RR 12.5 0.5 0.5 consanguineous marriages increase the risk of exposing a rare defective allele has led most cultures to make marriages between close relatives taboo....
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This note was uploaded on 04/29/2008 for the course GENE 310 taught by Professor Magill during the Spring '08 term at Texas A&M.

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Inbreeding - uncle niece, first cousins) there is a chance...

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