Adrenergic Receptor Allele Frequencies and HaplotypesAll mutations observed coincided with the Hardy-Weinberg equilibrium. Haplotype frequencies were determined on the basis of the results obtained from 37 unrelated subjects. The results are displayed in table tab:haplotypes.
Table 4.8: Alleles of the human 
adrenergic
receptor
The degree of polymorphism of a marker may be assessed by the proportion
of individuals in the population who are heterozygous for that marker. In other
words, the probability, that a random individual is heterozygous is used as a
measure of the degree of polymorphism. This probability may be estimated in two
principal ways: The first measure is the amount of heterozygosity observed
and is simply the proportion of heterozygous individuals observed in
the sample [152]. In human genetics, a more precise estimate is used. It
rests on the assumption that the genotypes are in
Hardy-Weinberg equilibrium . This expected heterozygosity is defined as
, where the sum is taken over all alleles, with
denoting the frequency of the i-th allele. The maximum
likelihood estimate of h is given by 
and is slightly biased. An unbiased estimate is 
, where n is the number of alleles observer in a sample
[153]. The estimate 
is preferable over 
because
it is unbiased and has a smaller mean square error than
.
An older measure of heterozygosity is the Polymorphism Information Content (PIC ) value [154], which is defined as
where a is the number of alleles at the given locus. For family data PIC may be somewhat more appropriate, whereas the heterozygosity is more general.
Heterozygosity and the calculated Polymorphism Information Content (PIC) are shown in table tab:pic.
Table 4.9: PIC and of the scanned mutations