mothur

Create "fake" contigs from short reads

Hi,
I was wondering if still the data would be processed correctly, if I know that some read-pairs may be too short to overlap.

Let’s say I have a read pair:
read1: AAACCC(...)TTTGGG
read2: CCCAAA(...)CCCGGG (already reversed)

and I know they are too short to overlap and clearly make.contigs will merge them incorrectly so to not lose this data I could “glue” them manually to create such contig:
AAACCC(...)TTTGGGNNNNNNNNNNNNNNNNNNNNCCCAAA(...)CCCGGG

and then I’d mix such contigs with the other “correct” contigs created by make.contigs.

Is it really idea to use the data like this?

I don’t think that this is a good idea. For one thing, if you include Ns then your sequences should be kicked out again in a proper “screen.seqs” step that eliminates every sequence with ambiguities.

so there is no option to make kind of “split alignment”?
lets say I have V3 and V4 region and forward/reverse reads:
-------3333333333333333------------------44444444444444444444--------
-------FFFFFFFFFFFFFFFFnnnnnnnnnRRRRRRRRRRRRRRRRR------
--------FFFFFFFFFFFFFFFnnnnnnnnnnRRRRRRRRRRRRRRRRRR------

As I suspect some of my reads won’t overlap into contig, but I don’t need to cover the full non-variable region between V3-V4. It would be just enough to keep track that the 1st read aligned to V3, the 2nd read aligned to V4. Is it bad idea?

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