Frequency variation of repeat-number allelic variation at a microsatellite locus
The modal repeat number in this population is 9.
Alternative alleles are produced by slipped-mismatch
replication, which creates new alleles that
differ by a single repeat unit from the parent. Models
of population variation often assume that each
allelic repeat class has arisen only once, for example
that the 8- and 10-fold repeats
originated rom the 9-fold repeat, and are thus
separated by two mutations events. However, since
slipped-mismatch can cause either loss or gain of a
repeat unit, the same allele may be generated more than
once. For example, a 9 allele may gain a repeat
to produce a 10 allele, and subsequently lose a
repeat so as to appear identical to the ancestral 9
allele, even though it differs by two mutations.
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