From Nature:
Scientists in Israel have pinpointed a common genetic trait that could make some of us hungrier for sex than others. The team looked at a gene known as the dopamine D4 receptor (DRD4), which partly controls the brain’s response to dopamine, a chemical often associated with the body’s ‘pleasure system’. Scientists know that this neurotransmitter can control sexual behaviour in animals and humans, and that dopamine circuits help to create the drive for things such as sex, drugs and food. Richard Ebstein at the Hebrew University in Jerusalem was prompted to examine the DRD4 gene after a 2004 study showed that a drug blocking this gene’s function helped to trigger erections in rats.
Ebstein and his colleagues asked 148 male and female college students to fill in a sex questionnaire that posed questions such as ‘How important is sex in your life?’ and ‘How often do you have sexual fantasies?’ The researchers found that students with one particular version of the gene scored roughly 5% lower, on average, in sexual desire than those with an alternative gene variant; a small but statistically meaningful difference. Around 70% of the population carry the low-arousal version and some 20% carry the high-arousal version of the gene.
More here.