How to represent variants is a whole can of worms. There are a number of competing systems.

* RSIDs (from DBsnp https://www.ncbi.nlm.nih.gov/snp/) * HGVS as mentioned. * Ensembl chrom-pos-ref-alt (CPRA). * Variant key (Nicola Asuni)

As dasmoth says, there is no fixed coding sequence for a gene or location in the genome.