More than one locus
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The attainment of equilibrium in genotype frequencies after one generation of random mating is true of all autosomal loci considered individually.
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But it is not true of the genotypes considered jointly .
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Consider a population made up of equal numbers of AABB and aabb individuals of both sexes. The gene frequency at both loci is 0.5.
- If the individuals are mated at random the possible genotypes are:
AABB
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AaBB
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aaBB
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AABb
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AaBb
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aaBb
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AAbb
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Aabb
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aabb
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Only three out of nine genotypes would appear in the progeny in the next generation i.e. the two original homozygotes ( AABB and aabb ) and the double heterozygote ( AaBb ).
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The genotype AAbb would be absent though its frequency in equilibrium population would be 1/16.
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The missing genotypes appear in subsequent generations but not immediately at their equilibrium frequency.
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Therefore when two loci are considered together the genotype frequencies will reach equilibrium after several generations of random mating.
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If three loci are considered together, then the number of generations required to reach equilibrium genotype frequencies will be more than that required for two loci considered jointly.
Linked loci
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Last modified: Tuesday, 26 July 2011, 5:52 AM