In genetic research I often come across references to single-nucleotide polymorphisms (SNPs). An example is rs3184504(C;T)
. As far as I understand it: In this case rs3184504
refers to a specific point in the DNA genome, and (because this one occurs in a non-sex human chromosome) it indicates the nucleotides at that point in each copy of that chromosome.
But how does one determine which strand of the DNA helix it references? Is there a convention? Or is the strand indicated in the SNP reference (in this case rs3184504
)?
If one strand is C;T
then the opposing strand will be G;A
... but in the context of the gene in question I assume it matters which strand is referenced in the SNP. E.g., if the code following this SNP on the chromosome in which rs3184504
has C
is:
CTCGA...
GAGCT...
this is a different genotype from the SNP indicating a C
on the other strand:
GTCGA...
CAGCT...
So the SNP description is only meaningful if it also indicates the strand, right? If so, how does the SNP descriptor do that?