Fig. 3.

The difference between adding a true variant and adding an artifact in generated reads. (A) Adding an artifact is relatively easy as all the tool has to do is to modify the base at the wanted position without touching the read’s UMI tag. (B) On the other hand, in order to add a true variant, the software must change the base at the wanted position on a set of reads. Then it will create a new UMI tag (UMI tag 3) and change the UMI tag of all the affected reads to UMI tag 3.