Scientists may have found genetic indicators of whether someone has same or opposite-sex attraction.
The link was discovered when scientists compared the DNA of 47 sets of male twins. The pairs included some where the two twins had a different sexual orientation.
Looking at the molecular data from nine genome sites, researchers could guess whether a twin pair was straight or gay with up to 70% accuracy. Lead researcher Dr Tuck Ngun, from the University of California at Los Angeles, said: “To our knowledge, this is the first example of a predictive model for sexual orientation based on molecular markers.”