# Aligned base strand in pysam pileupcolumn

Is it possible that on the same pileupcolumn object (i.e a specific aligned base) I find the same base but aligned to different strands? For example, can I find a coverage of 50 'A's that align to strand '+', and on the same time 50 'A's that align to strand '-' within the same index? I expect that if 'A' is aligned to strand '+', I will find 'T' aligned to strand '-'.

• Please edit your question and clarify what you are doing. What code are you running? On what input? Anything is possible, including mismatched bases either in the real data or because of a sequencing error, but we can't know if you don't give us more details. – terdon Mar 26 '19 at 14:55