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7
Analysis of genotypic structure
The following measures and tests aid in the characterization of genotypic structures. In
contrast to other measures quantifying variation within and between samples (see Sec.
6, 8), heterozygosity measures genetic variation within individuals. Tests of single locus
structure investigate the association of gametes in observed (zygotic) genotypic structures
by comparing the observed structures to the corresponding expected structures under
certain models of association.
7.1
7.1.1
Heterozygosity
Proportion of heterozygosity of single-locus genotypes
Given the genotypes of all individuals in a collection at a single gene locus, the proportion
of heterozygosity equals the proportion of heterozygous individuals in the collection.
Reference: [16]
7.1.2
Conditional heterozygosity of single-locus genotypes
The conditional heterozygosity at a single gene locus takes into account that the proportion of heterozygosity is conditional on the allele frequencies. It results from division
of the actual heterozygosity (= proportion of heterozygosity at a single locus) by the
corresponding maximum proportion of heterozygosity Hmax obtainable for the underlying
allele frequencies, where Hmax equals 1 if all allele frequencies are less than or equal to
0.5 and Hmax = 2(1 − p) if the most frequent allele has frequency p greater than 0.5.
References: [6], [16]
7.1.3
Degree of heterozygosity of multilocus genotypes
The degree of heterozygosity is defined for an individual with respect to a specified
number of gene loci, and is identical to the proportion of loci at which this individual is
heterozygous. The average degree of heterozygosity refers to the distribution of this
degree in a collection of individuals. Hence it can be proven that the average degree of
heterozygosity equals the mean proportion of heterozygotes at the single loci.
Reference: [6]
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