Tweet
Yep, your reads were already adapter-trimmed. Some versions of Illumina software will do this on the machine if configured to do so. I don't recommend that, though, as it's less accurate. Re-trimming does not really hurt, but it's always best to start with the raw data.
Merging is even more useful because of the high proportion of short reads - those are the ones that overlap 100%, and thus get fully error-corrected when merged because each base was called twice. So, you should certainly do it. The reads under 150bp had adapter sequence detected by Illumina's software, meaning they had insert sizes under 150bp.
Unlike most other platforms, Illumina reads all come out from the machine the same length (in this case 150bp) unless they are explicitly trimmed during a post-processing step.
Merging is even more useful because of the high proportion of short reads - those are the ones that overlap 100%, and thus get fully error-corrected when merged because each base was called twice. So, you should certainly do it. The reads under 150bp had adapter sequence detected by Illumina's software, meaning they had insert sizes under 150bp.
Unlike most other platforms, Illumina reads all come out from the machine the same length (in this case 150bp) unless they are explicitly trimmed during a post-processing step.
Comment