Scientists have found two stretches of DNA linked to
homosexuality in men.
The confirmation of the existence of a ‘gay gene’ or genes
will strengthen arguments that homosexuality is a matter of biology, rather than
choice.
However, it also raises the prospect of a genetic test that
could be used by insurance companies to discriminate against clients or by
pregnant women to abort gay babies.
In the study, Chicago University researchers analysed the
DNA of more than 400 pairs of gay brothers, recruited at Gay Pride festivals at
marches over several years.
This revealed flagged up two pieces of DNA that seem to be
linked to homosexuality.
It is not known which of the many genes they contain are key
or how they affect the development of sexual orientation.
However, the result, revealed at the American Association
for the Advancement of Science’s prestigious annual conference, backs up a
contentious 1993 study.
That research, the first to find evidence of a ‘gay gene’,
created a storm of controversy, which was further fuelled when other scientists
failed to find a genetic link.
Dr Michael Bailey from Northwestern University in Illinois,
who contributed to the latest study, said it is the biggest of its kind.
He added: ‘Sexual orientation has nothing to do with choice.
Our findings suggest there may be genes at play – we found evidence for two
sets that affect whether a man is gay or straight.
‘Although this could one day lead to a pre-natal test for
male sexual orientation, it would not be very accurate, as there are other
factors that can influence the outcome.’
Despite this, he would not would not object to a prenatal
test being developed.
He said: ‘Clearly parents should not be allowed to torture
or kill babies. But they can currently choose to terminate a pregnancy early
on, so they should be allowed to have as much information on the future child
as possible.’
Qazi Rhaman, a King’s College London psychologist, said that
genes are thought account for up to 40 per cent of a person’s sexual
orientation is governed by genes, and that it is likely that many genes are
involved.
This would make developing a genetic test incredibly
difficult.
He said: ‘There is no real risk of anyone finding a 'genetic
test' for sexual orientation based on these or any of the scientific findings
about the genetics of sexuality from the past 20 years.
‘The reason is that there is no gay gene. You are not going to be able to develop a
test to find them all.’
Dr Rhaman, who has written a book about sexual orientation,
added that all psychological traits involve genetics and people should not be
afraid about link homosexuality to genes.
Richard Lane, of gay rights organisation, Stonewall, said
that while studies into the origins of homosexuality have yet to produce
convincing evidence, they do to point to a biological root.
He said: ‘The thing that’s consistent across all of them is
that they all point to sexual orientation being something fundamental to a
person rather than the lifestyle choice some opponents of equality repeatedly
suggest.’
Other studies suggests that conditions in the womb also
influence sexual orientation.
For instance, the more older male siblings a man has, the
greater chance he will be gay.
Scientists say the phenomenon cannot be explained by the
youngest boy being babied and mollycoddled or other differences in the way they
are brought up.
It is thought that carrying a male baby in the womb triggers
an immune response in the mother, creating antibodies that attack part of the
unborn child's brain linked to sexual orientation.
This response gets stronger the more boys a woman carries,
raising the odds of homosexuality.
Exposure to hormones in the womb is also likely to be
important and some argue that upbringing plays a role in sexuality.
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