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Unformatted text preview: the brother-sister mating will be homozygous for the deleterious allele is 1/4 3 1/4 5 1/16. There are so many rare deleterious alleles for different genes in the human populations that each one of us is a heterozygote for many such rare alleles. Thus the chances are very high that an offspring of a brother-sister mating will be homozygous for at least one of them. Systematic inbreeding between close relatives even- tually leads to complete homozygosity of the population but at different rates, depending on the degree of rela- tionship. If two alleles are present in an inbreeding pop- ulation, one will eventually be lost and the other will have a frequency of 1.0—in other words, it will become fixed. For alleles that are not deleterious, which allele will become fixed is a matter of chance. Suppose, for ex- ample, that several groups of individuals are taken from a population and subjected to inbreeding. If, in the origi- nal population from which the inbred lines are taken, al- lele A has frequency p and allele a has frequency q 5 1 2 p, then a proportion p of the homozygous lines established by inbreeding will be homozygous A/A and a proportion q of the lines will be a/a. Inbreeding takes the genetic variation present within the original popula-...
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.
- Spring '08