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Why GWASs cannot speculate what kind of mutation the SNP would cause?

I am trying to understand results from GWAS studies, and I have this question:

Why can't GWAS studies speculate about what kind of consequence would the specific SNP have? As they information about the precise position on the genome + which base changes, I thought studies would speculate if the SNP in question causes a silent/missense/nonsense mutation, but they apparently do not (at least those I have read).

I guess some information is missing or uncertain to speculate about that... What is it? I was thinking maybe which frame is read?

Any guess?

gwas snp

2 answers

Adding to the response by swbarnes2, many of the variants identified in GWAS are located in non-coding regions of the genome and will function not by altering the protein coding sequences, but by regulation of gene expression.

My assumption is that generally the "lead" SNPs identified as most significant in GWAS are not necessarily the actual causal SNP because of linkage disequilibrium. Therefore trying to ascertain a function or effect of those SNPs would be misleading. I believe they generally try to do further studies on implicated loci (called "fine-mapping") to more precisely locate the likely causal variants (e.g., pmid: 26551672).

Great point! Thanks for the addition, Collin!

It's easy to predict the amino acid change consequence of a mutation. What's hard is to predict the functional consequences of most changes.

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