Introduction to Genetic Analysis 622

Introduction to Genetic Analysis 622 - 44200_19_p611-642...

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19.2 Effect of sexual reproduction on variation Meiotic segregation and genetic equilibrium If inheritance were based on a continuous substance like blood, then the mating of individuals with different phe- notypes would produce offspring that were intermediate in phenotype. When these intermediate types mated with each other, their offspring would again be interme- diate. A population in which individuals mated at ran- dom would slowly lose all its variation, and eventually every member of the population would have the same phenotype. The particulate nature of inheritance changes this picture completely. Because of the discrete nature of genes and the segregation of alleles at meiosis, a cross of intermediate with intermediate individuals does not re- sult in all intermediate offspring. On the contrary, some of the offspring will be of extreme types—those that are homozygotes. Consider a population in which males and females mate with one another at random with respect to some gene locus A ; that is, the genotype at that locus is not a factor in choosing a mate. Such random mating is equivalent to mixing all the sperm and all the eggs in
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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.

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