What this means

OR7D4 is an olfactory receptor that responds strongly to androstenone, a steroid found in male pig saliva and in human sweat. People with two functional copies tend to find the smell unpleasant; people with two non-functional copies often can't smell it or describe it as pleasantly woody. This is one of the cleanest demonstrations that the same molecule can be a completely different sensory experience depending on which receptor variant you carry.

OR7D4 is a smell receptor that reacts to androstenone — a steroid found in male pig saliva and in human sweat. People with two working copies usually find the smell pretty unpleasant. People with two broken copies often can't smell it at all, or describe it as faintly woody or sweet. It's one of the clearest examples in genetics that the exact same molecule can smell like completely different things to different people, depending on which receptor version they carry.

Caveats

• Concentration matters: even "non-smellers" pick up androstenone at very high levels.
• Cultural context shapes how a smell is labelled (pleasant vs unpleasant).
• Most studies have focused on European-ancestry participants.
• The receptor explains only part of the variation in androstenone perception.

References

• Keller et al. — Genetic variation in a human odorant receptor alters odour perception (Nature, 2007)
• Lunde et al. — Genetic variation of an odorant receptor OR7D4 and sensory perception of cooked meat containing androstenone (PLOS ONE, 2012)