At the bottom of Table 1 (Allele Frequencies) is given the value for Hobs, which

Question

At the bottom of Table 1 (Allele Frequencies) is given the value for Hobs, which stands for “observed heterozygosity,” because the heterozygosity observed often differs from what you expect. Think of heterozygosity as being the (expected) probability that an individual will be heterozygous at a given locus. What H is expected is calculated as follows. The number of possible genotypes at a locus can be calculated using the formula k(k+1)/2, where k is the number of alleles at a particular locus. So, for example, one loci having two alleles (A, a) gives rise to three possible genotypes (AA, Aa, aa). The parameter k also represents the expected number of homozygous genotypes, and the total number of genotypes minus the number of homozygous genotypes equals the number of heterozygous genotypes. Or, put in equation form: k[(k-1)/2] represents the expected number of heterozygous genotypes. The percentage of individuals heterozygous for a given locus (i.e. the heterozygosity) is calculated from the allele frequencies, assuming independent assortment. If the observed heterozygosity equals the expected heterozygosity, HOBS = 1. For each of the three loci examined in this lab HOBS is less than 1.0, meaning there are fewer heterozygotes than expected. Explain, in the space remaining on this page, what this says about population dynamics.

Explanation / Answer

* A decrease in heterozygosity implies that there is high rate of inbreeding in the population. This can also be attributed to reduced random mating, subdivision of population into isolated and differentiated reproductive units (wahlund effect).

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