Question: Mapping DNAseq reads on cds ?
0
gravatar for thomasbersez
5 weeks ago by
thomasbersez10
France INRA
thomasbersez10 wrote:

It may be a dumb question but, does anyone know a method / tool to map DNAseq reads to cds ? Reads falling in between exon and intro may have to be automatically trimmed. Thanks for help.

next-gen alignment • 112 views
ADD COMMENTlink written 5 weeks ago by thomasbersez10
2

Reads falling in between exon and intro may have to be automatically trimmed.

Reads in that region will fail to map if you are only aligning against CDS sequences in your reference. Aligners will generally soft clips reads (if the alignment ends partway in the read).

What exactly are you wanting to do?

ADD REPLYlink written 5 weeks ago by genomax62k

I am developing a pipeline for variant calling on wild relative of cultivated plants. The overall idea is to find cds variants in wild specie. Because wild specie genome isn't always available, I may to map my DNAseq read onto cds of the gene(s) of interest.

Thanks for the answer!

ADD REPLYlink written 4 weeks ago by thomasbersez10

It is doable with BWA or Bowtie2. The main issue is that you'll need to tweak the gap parameters to assign a very low penalty to gaps, since I guess that some of your CDS are entire mRNA without the introns.

In BWA you might be interested in the following parameters:

  • -O INT Gap open penalty. [6]
  • -E INT Gap extension penalty. A gap of length k costs O + k*E (i.e. -O is for opening a zero-length gap). [1]
  • -L INT Clipping penalty. When performing SW extension, BWA-MEM keeps track of the best score reaching the end of query. If this score is larger than the best SW score minus the clipping penalty, clipping will not be applied. Note that in this case, the SAM AS tag reports the best SW score; clipping penalty is not deducted. [5]

Source: http://bio-bwa.sourceforge.net/bwa.shtml

Starting from there, I think it is just trial and error to find the correct parameters

ADD REPLYlink modified 5 weeks ago • written 5 weeks ago by Gautier Richard240
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