I mapped reads (stranded library prep) with STAR to my reference genome and learned, that you can count reads, which aligned to the forward or reverse strand of the reference seuquence, using the FLAG option.
Reads mapped to Forward strand
samtools view -c -F 20 FILE.bam >> Output_file.txt
Reads mapped to Reverse strand
samtools view -c -f 16 FILE.bam >> Output_file.txt
This showed me in all files a strong inbalance of read distribution between the strands, which I did not expect, with a few hundred thousend reads on the plus strand and a few million reads on the reverese strand. The library preparation should not make any difference in this, that's why I am wondering, if I may have something wrong in the code?
There are no multimappers in the data and the data only comes from mitochondrial RNA.
Edit: a word