rs5020278

rs5020278, a SNP in the OR7D4 olfactory receptor gene, is associated with how individuals perceive the smell of a testosterone-derived steroid, androstenone. This SNP is also known as T133M as it causes a change at amino acid 133 of the OR7D4 protein from threonine to methionine. In the orientation reported for this SNP in dbSNP, most individuals (~75%) are homozygous for rs5020278(G), and perceive this steroid as smelling either strongly sweaty or like urine. Individuals with one or two copies of rs5020278(A) perceive the smell to be both weaker, and more sweet, with some likening it to vanilla or honey. Genetic variation in a human odorant receptor alters odour perception. A common variant of the receptor OR7D4, OR7D4 WM contains two non-synonymous single nucleotide polymorphisms (SNPs), resulting in two amino acid substitutions (R88W, T133M; hence 'RT') that severely impair function in vitro. Human subjects with RT/WM or WM/WM genotypes as a group were less sensitive to androstenone and androstadienone and found both odours less unpleasant than the RT/RT group.