rs1800747, also known as IVS17-1G>A, c.5075-1G>A and then also IVS17-1G>C and c.5075-1G>C, is a variant in the BRCA1 gene. The common G allele can mutate to all three possibilities: G>A, G>C, and G>T. All are rare. Currently the G>A and G>C alleles are considered pathogenic in ClinVar for breast cancer .
In addition to rs1800747, this SNP is represented on 23andMe microarrays as i5009520 and i5009521, respectively, for the G>A and G>T alleles.