Homosexuality linked to genes: Ethical dilemmas loom as genetic study of gays' families suggests predisposition is inherited through men's mothers

SCIENTISTS have found the first hard evidence of a genetic basis for homosexuality. They believe they will be able in a few years to isolate a 'gay gene' that men inherit from their mothers.

The research, published in the journal Science, raises ethical issues on the genetic influences on human sexual preferences. Finding a gene that predisposes a person to homosexuality could soon lead to pre-natal diagnostic tests which might in theory be offered to pregnant women to determine whether to abort a foetus carrying the gene.

Unusually, the researchers make a plea at the end of their research paper for such information about genetic predispositions not to be used to discriminate against sexual preferences: 'We believe that it would be fundamentally unethical to use such information to try to assess or alter a person's current or future sexual orientation, either heterosexual or homosexual, or other normal attributes of human behaviour.' The scientists, led by Dean Hamer, an Aids researcher at the US National Cancer Institute near Washington DC, said: 'Scientists, educators, policy makers and the public should work together to ensure that such research is used to benefit all members of society.'

Although they feel confident of being able to identify one or more genes involved in a tendency towards homosexuality, the scientists emphasised that their findings cannot explain all male homosexuality. Dr Hamer said it is likely homosexuality arises from a variety of causes, both genetic and environmental.

Other research groups had found that homosexual preferences sometimes tend to run in families, indicating a genetic basis, but the latest research has located a region of the X chromosome - which men inherit from their mothers - that is strongly implicated.

Dr Hamer and colleagues studied the family histories of 114 homosexuals and found that 13.5 per cent of the gay men's brothers were also homosexual, compared with 2 per cent in the general population. They also found maternal uncles and maternal male cousins were more likely to be homosexual. In some families, gay relatives could be traced back three generations. Because homosexual uncles and male cousins of the gay subjects were raised in different households, the scientists hypothesised a genetic factor on the X chromosome was responsible.

They analysed the X chromosomes of 40 pairs of gay brothers using genetic markers, which are like signposts. They found that 33 of the paired brothers had coinherited genetic markers on the same region of the X chromosome, known as Xq28.

This region represents only 0.02 per cent of the human genome - the entire genetic makeup - but may carry several hundred genes, so there is considerable work to be done to identify the precise gene, or genes, involved, Dr Hamer said.

'Our research implies that being gay or straight relies to some extent on a genetic predisposition. We can only speculate on what the gene does. Once we have the gene, we'll be able to understand it,' he said.

The scientists do not know why seven of the 40 pairs of gay brothers do not appear to have the same genetic markers.

Dr Hamer said these gay men may have inherited other genes that are associated with homosexuality, or they might have been influenced by 'environmental factors or life experiences'.

In 1991, Simon LeVay, a British-born scientist at the Salk Institute for Biological Studies at San Diego, California, found slight structural differences in the hypothalamus of the brains of gay men. Other reseachers have also identified structural differences in other areas of the brain, but were not able to say whether this resulted from environmental influences or genetic inheritance.

Opening a Pandora's box, page 3

Leading article, page 19

Start your day with The Independent, sign up for daily news emails
Have you tried new the Independent Digital Edition apps?
ebooksA celebration of British elections
Arts and Entertainment
Billie Piper as Brona in Penny Dreadful
tvReview: It’s business as usual in Victorian London. Let’s hope that changes as we get further into the new series spoiler alert
Arts and Entertainment
Sarah Lucas, I SCREAM DADDIO, Installation View, British Pavilion 2015
artWhy Sarah Lucas is the perfect choice to represent British art at the Venice Biennale
Arts and Entertainment
No Offence
tvReview: No Offence has characters who are larger than life and yet somehow completely true to life at the same time spoiler alert
Chuck Norris pictured in 1996
  • Get to the point
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

SThree: Trainee Recruitment Consultant - Dublin

£13676.46 - £16411.61 per annum + OTE: SThree: SThree Trainee Recruitment Cons...

Ashdown Group: Marketing or Business Graduate Opportunity - Norwich - £22,000

£18000 - £22000 per annum + training: Ashdown Group: Business and Marketing Gr...

SThree: Trainee Recruitment Consultant

£20000 - £25000 per annum + Commission: SThree: Are you great at building rela...

Ashdown Group: Database Analyst - Birmingham - £22,000 plus benefits

£20000 - £22000 per annum + excellent benefits: Ashdown Group: Application Sup...

Day In a Page

General Election 2015: Ed Miliband's unlikely journey from hapless geek to heart-throb

Miliband's unlikely journey from hapless geek to heart-throb

He was meant to be Labour's biggest handicap - but has become almost an asset
General Election 2015: A guide to the smaller parties, from the the National Health Action Party to the Church of the Militant Elvis Party

On the margins

From Militant Elvis to Women's Equality: a guide to the underdogs standing in the election
Amr Darrag: Ex-Muslim Brotherhood minister in exile still believes Egypt's military regime can be replaced with 'moderate' Islamic rule

'This is the battle of young Egypt for the future of our country'

Ex-Muslim Brotherhood minister Amr Darrag still believes the opposition can rid Egypt of its military regime and replace it with 'moderate' Islamic rule, he tells Robert Fisk
Why patients must rely less on doctors: Improving our own health is the 'blockbuster drug of the century'

Why patients must rely less on doctors

Improving our own health is the 'blockbuster drug of the century'
Sarah Lucas is the perfect artist to represent Britain at the Venice Biennale

Flesh in Venice

Sarah Lucas has filled the British pavilion at the Venice Biennale with slinky cats and casts of her female friends' private parts. It makes you proud to be a woman, says Karen Wright
11 best anti-ageing day creams

11 best anti-ageing day creams

Slow down the ageing process with one of these high-performance, hardworking anti-agers
Juventus 2 Real Madrid 1: Five things we learnt, including Iker Casillas is past it and Carlos Tevez remains effective

Juventus vs Real Madrid

Five things we learnt from the Italian's Champions League first leg win over the Spanish giants
Ashes 2015: Test series looks a lost cause for England... whoever takes over as ECB director of cricket

Ashes series looks a lost cause for England...

Whoever takes over as ECB director of cricket, says Stephen Brenkley
Fishing for votes with Nigel Farage: The Ukip leader shows how he can work an audience as he casts his line to the disaffected of Grimsby

Fishing is on Nigel Farage's mind

Ukip leader casts a line to the disaffected
Who is bombing whom in the Middle East? It's amazing they don't all hit each other

Who is bombing whom in the Middle East?

Robert Fisk untangles the countries and factions
China's influence on fashion: At the top of the game both creatively and commercially

China's influence on fashion

At the top of the game both creatively and commercially
Lord O’Donnell: Former cabinet secretary on the election and life away from the levers of power

The man known as GOD has a reputation for getting the job done

Lord O'Donnell's three principles of rule
Rainbow shades: It's all bright on the night

Rainbow shades

It's all bright on the night
'It was first time I had ever tasted chocolate. I kept a piece, and when Amsterdam was liberated, I gave it to the first Allied soldier I saw'

Bread from heaven

Dutch survivors thank RAF for World War II drop that saved millions
Britain will be 'run for the wealthy and powerful' if Tories retain power - Labour

How 'the Axe' helped Labour

UK will be 'run for the wealthy and powerful' if Tories retain power