of random mating within each population, however, each of them will have the same genotypic frequencies: and they will remain so indeFnitely. One consequence of the Hardy-Weinberg propor-tions is that rare alleles are virtually never in homozy-gous condition. An allele with a frequency of 0.001 is present in homozygotes at a frequency of only 1 in a million; most copies of such rare alleles are found in het-erozygotes. In general, two copies of an allele are in homozygotes but only one copy of that allele is in each heterozygote, so the relative frequency of the allele in heterozygotes (in contrast with homozygotes) is, from the Hardy-Weinberg equilibrium frequencies, a / a q 2 5 (0.7) 2 5 0.49 A / a 2 pq 5 2(0.3)(0.7) 5 0.42 A / A p 2 5 (0.3) 2 5 0.09 The Hardy-Weinberg Equilibrium BOX 19-2 If the frequency of allele A is p in both the sperm and the eggs, and the frequency of allele a is q 5 1 2 p , then the consequences of random unions of sperm and eggs are as shown in the adjoining diagram. The
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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.