How deletions can change homogeneous mutation genotype to heterogeneous mutation genotype(deletion:2->1)?

[phoebe-xin-leung]

dear sir:
I'm reading your work of SiFiT, that's a briliant work. However, I cannot make sense that how deletions can change homogeneous mutation genotype to heterogeneous mutation genotype ( 2 ->1 ), as you mentioned in the article that "deletions can result in the genotype transitions 1→0, 1→2, or 2→1 ......". As far as I know it can be impossible to happen.