Question: BWA MEM and ancient DNA
5
gravatar for smilefreak
4.5 years ago by
smilefreak400
New Zealand
smilefreak400 wrote:

Hi, 

I have been doing some ancient DNA bioinformatics for a while now and have been using the bwa aln command. 

When using this command with ancient DNA it is recommended to disable seeding. This slows down alignments somewhat but allows the damaged DNA sequences to be aligned, the characteristic damage is a C->T transition at the 3' end of the sequenced fragments.  For instance I use the parameters -l 1024 (to disable seeding) -o 2 (increase gap open slightly) and -n 0.03 (reduce the edit distance slightly). These parameters were taken from this paper

http://www.biomedcentral.com/1471-2164/13/178


My question:

Are there any specific settings required to use bwa mem with ancient DNA?
Does bwa mem use seeding at all? 

Thanks in advance

alignment adna • 2.9k views
ADD COMMENTlink modified 4.3 years ago by usmanroshan10 • written 4.5 years ago by smilefreak400
3
gravatar for Istvan Albert
4.5 years ago by
Istvan Albert ♦♦ 80k
University Park, USA
Istvan Albert ♦♦ 80k wrote:

I had really good experiences with bwa mem when using it on dataset with high error rates. It far outperformed other tools. See this:

A: When and why is bwa aln better then bwa mem?

Your problem seems to be very similar in nature in that it introduces mismatches that are similar to sequencing errors. From what I understood from the paper bwa mem was designed to be robust to this type of errors.

ADD COMMENTlink modified 4.5 years ago • written 4.5 years ago by Istvan Albert ♦♦ 80k
1
gravatar for usmanroshan
4.3 years ago by
usmanroshan10
usmanroshan10 wrote:

Hi, you may want to try the GPU program MaxSSmap that is designed for aligning divergent reads to genomes. http://www.biomedcentral.com/1471-2164/15/969/abstractWe used it to map ancient DNA reads and compared to BWA MEM it produced many more high quality alignments. You may also want to look into NextGenMap which also achieved a higher mapping rate BWA MEM.

ADD COMMENTlink modified 4.3 years ago • written 4.3 years ago by usmanroshan10
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