This might be a very basic question for many here. With the basic understanding of inheritance, eventhough there is a possibility of multiple genotypes due to multi alleles, the resulting genotype can only have two alleles(paternal and maternal) that way after variant calling, an allele at one position can be homozygous or heterozygous. So there can be max of two alleles, but why do we see multiple alleles at a given position in single sample VCF. I am trying to understand the science behind this. Please help out. Thanks!
chr5 127640782 . AG A,AA . . . GT:AD:DP 1/2:0,28,409:437