Geneticists claim that female mice can be turned 'lesbian' by a single gene deletion.
The researchers found that disabling the fructose mutarotase (FucM) gene in female mice causes them to avoid male advances and instead attempt to mate with other females, BMC Genetics reports.
Research leader Professor Chankyu Park and his team from the Korea Advanced Institute of Science and Technology, believe that disabling the gene exposes parts of the brain linked with sexual preference in adult life to additional oestrogen levels.
'The mutant female mouse underwent a slightly altered developmental program in the brain to resemble the male brain in terms of sexual preference', explained Professor Park.
The team showed that after forced mating with 'normal' males, the FucM females were fertile, but were not sexually receptive. The mutant female mice also lost interest in investigating male urine, unlike non-genetically altered females.
Professor Park speculated that 'these behavioural changes are likely to be related to a neurodevelopmental change in a pre-optic area of the female mutant brain, becoming similar to that of a normal male'.
In a normal female mouse fetus, additional oestrogen would be filtered out via a substance known as alpha-fetoprotein (AFP). However this only functions correctly when accompanied with fructose. Consequently, without the gene that makes the enzyme, AFP cannot regulate oestrogen levels.
Professor Park and his team are hoping to use screening studies to investigate the influence of gene deletion on human sexual orientation, although he admits this research may be 'very difficult', partly due to difficulties in finding a suitable number of volunteers.
Dr Simon LeVey, lecturer in the origins of sexuality from Stanford University, says the study is not directly relevant to the subject of human sexual preference. As he explains, it is testosterone not oestrogen that masculinises the human brain and human AFP doesn't prevent oestrogen from entering the brain as it does in mice.
'Nevertheless, it is probably only a matter of time before molecular geneticists identify genes that influence sexual orientation in humans', says Dr LeVay.
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