Ok, thanks. I'll try that...
Hi- I need a reliable method to identify SNPs in the human genome with the most variability. Does anyone know of a data file I can download (a VCF or something easy to parse) that contains snps and a conservation score like PhyloP or PhastCons?
In lieu of that if you can recommend something to identify the least conserved regions I could pick SNPs from those regions.
Thanks.
2 answers
Download dbSNP and convert from VCF to BED with BEDOPS
vcf2bed.$ vcf2bed < (gunzip -c dbSNP.vcf.gz) > dbSNP.bedDownload phyloP44 or other alignments and convert from WIG to BED with BEDOPS
wig2bed.$ wig2bed < (gunzip -c phyloP.wig.gz) > phyloP.bedFile names will depend on what you download from NCBI and UCSC Goldenpath.
Map signal (score) to SNPs with BEDOPS
bedmap:$ bedmap --echo --echo-map-score --skip-unmapped --delim '\t' dbSNP.bed phyloP.bed > answer.bedRead
answer.bedinto R withread.table()and find the population of signals/scores for all mapped variants. You should be able to get the minimum-scoring variants from that distribution. Or usesort -nron the signal column andheadto get the minimum score, andawkto filteranswer.bedfor variants with that score.
There are answers on biostars to deal with parts 1 and 2. Should be easy to find with a little searching.
In terms of published data, A. Quinlans group performed a nice analysis and released the data properly for others to use. Kudos.
Data are in BED and Bigwig format so hopefully useful. You can perhaps take the inverse of the constrained regions and restrict to exons to find the regions you want (use bedtools or similar?).
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