Using allele frequencies, it allows for the calculation of heterozygosity, or genetic diversity, in a finite population and for the estimation of genetic distances between populations of interest.
The assumptions of the ISM are that (1) there are an infinite number of sites where mutations can occur, (2) every new mutation occurs at a novel site, and (3) there is no recombination.
[1][2][3] The term ‘site’ refers to a single nucleotide base pair.
[1] Because every new mutation has to occur at a novel site, there can be no homoplasy, or back-mutation to an allele that previously existed.
The four gamete rule can be applied to the data to ensure that they do not violate the model assumption of no recombination.
is the number of mutations found within a randomly selected DNA sequence (per generation),
When considering the length of a DNA sequence, the expected number of mutations is calculated as follows
[7] Multiple assumptions are applied to understanding the ISM in terms of genome evolution:[7]