I noticed that the SNP in dbSNP have the attribute 'strand', I was wondering what's the meaning of the strand because the DNA is complementary, the SNP in Watson strand can also be observed in Crick strand. And if one SNP is labeled in plus strand, can I map this SNP to the gene in minus strand when the chromosome location is proper?
I'm just a touch confused.
How can a SNP be on the antisense / -ve strand? If the opposite strand's base is to be complementary and therefore also a SNP, it seems redundant to label a strand..? I read that were are occasionally mismatch errors across the DNA helix in that A binds opposite C or G..? Is that the reason?
The SNP is of course on both strands, but was mapped to one strand or the other because one strand of DNA is sequenced against a template of the other strand. In other words, strand A was sequenced and a SNP was found and hence mapped to a position on strand A and incorporated into a chromosome map also on that same strand. It could be that there is a gene in that same region but on strand B and so the SNP appears to be on the opposite strand of the gene.