Illustration of the copy unit alleles and their distributions in a population. a). A CNV locus of diploid genome of sample 1 who has one copy of allele a, two copies of allele b, and one copy of allele c at the locus, b). Alleles of each sample are shown, c). Four copy unit alleles at a CNV locus are aligned. Difference among these alleles is characterized by bases at variable sites.