Your Good Health: Why is one ‘intil’ tw gay, the other straight? - Victoria Tim Colonist

Contents:

• SCIENTISTS FD DNA DIFFERENC BETWEEN GAY MEN AND THEIR STRAIGHT TW BROTHERS
• YOUR GOOD HEALTH: WHY IS ONE ‘INTIL’ TW GAY, THE OTHER STRAIGHT?
• GAY GEICS
• THE 'GAY GENE' IS A TOTAL MYTH, MASSIVE STUDY CONCLUS
• SOME RANDOM THOUGHTS ON ‘GAY GENE’ STUDI
• STUDY: DNA OF INTIL TWS CAN REVEAL WHO'S GAY
• GAY MEN TW STUDY
• LARGT STUDY OF GAY BROTHERS HOM ON 'GAY GEN'

SCIENTISTS FD DNA DIFFERENC BETWEEN GAY MEN AND THEIR STRAIGHT TW BROTHERS

In a study where scientists looked at the sexual aroal patterns of intil tws wh different sexuali—specifilly, where one was gay and the other was straight—they found that gay tws monstrated more genal aroal rponse to same-sex imag, whereas straight tws monstrated more aroal rponse to oppose-sex imag [2]. In theory, this means two people uld rry “gay gen, ” but both of them wouldn’t necsarily be gay pendg on certa environmental factors.

YOUR GOOD HEALTH: WHY IS ONE ‘INTIL’ TW GAY, THE OTHER STRAIGHT?

Tw pairs which at least one tw is homosexual were soliced through announcements the gay prs and personal referrals om 1980 to the prent. Two sets ntaed a pair of monozygotic tws nrdant for sexual orientatn wh the third triplet dizygotic and disrdant for homosexual orientatn.

GAY GEICS

Ngun reported that studyg the geic material of 47 pairs of intil male tws, he has intified “epigeic marks” ne areas of the human genome that are strongly lked to male dividuals, said Ngun, the prence of the distct molecular marks n predict homosexualy wh an accuracy of close to 70%.

Geicists suggt that together, the human genome and s epigenome reflect the teractn of nature and nurture -- both our fixed herance and our bodi’ flexible rpons to the world -- makg who we ’s study of tws don’t reveal how or when a male tak on the epigenomic marks that distguish him as homosexual. ”To fd the epigenomic markers of male homosexualy, Ngun, a postdoctoral rearcher at UCLA’s Geffen School of Medice, bed through the geic material of 47 sets of intil male tws. But the existence of tw pairs which one is homosexual and the other is not offers strong evince that somethg other than DNA alone fluenc sexual orientatn.

So they unleashed a mache learng algorhm on the data to search for regulari that distguished the epigenom of homosexual tw-pairs om tws which only one was ne pact regns sttered across the genome, they found patterns of epigenomic differenc that would allow a predictn far more accurate than a random gus of an dividual’s sexual orientatn, Ngun reported Thursday. McCarthy and other experts utned that the disvery of epigenomic marks suggtive of homosexualy is a far cry om fdg the of sexual distctive epigenomic marks observed by Ngun and his lleagu uld rult om some other blogil or liftyle factor mon to homosexual men but unrelated to their sexualy, said Universy of Utah geicist Christopher Gregg. But the existence of intil tw pairs which only one is homosexual “nclively suggt that gen don’t expla everythg, ” Bailey Ngun’s rearch needs to be replited larger studi of tws, advanc the fful procs of better unrstandg how — and when — a boy’s sexual orientatn velops, Bailey me on Twter @LATMelissaHealy and “like” Los Angel Tim Science & Health on rarely get ncer, now scientists thk they know whyThree rearchers w Nobel Prize chemistry for studi of DNA repairMars had a long-lastg seri of lak, NASA’s Cursy rover fds.

THE 'GAY GENE' IS A TOTAL MYTH, MASSIVE STUDY CONCLUS

Studi have shown that intil tws, if one tw is gay (the term “homosexual” is ed clil studi but is nsired offensive, so I won’t e further), then 30 per cent to 66 per cent of the intil tws also will be gay.

SOME RANDOM THOUGHTS ON ‘GAY GENE’ STUDI

However, an adopted siblg of a gay person is also more likely to be gay (11 per cent one study), suggtg that the faial environment also plays a signifint role. “The people participatg our study are terted ntributg to this kd of scientific knowledge and want to unrstand at least part of how they me to be the way they are, ” Sanrs search for ‘gay gen’ go back to 1993, when a US team led by Dr Dean Hamer scribed a regn of DNA loted on the X chromosome lled Xq28.

“Conservative, right-wg people hated bee they felt that was sayg that beg gay is like beg black, that was -born, that would somehow ‘exce’ gay people or give them more rights, ” says Hamer.

“On the other hand, gay people hated too bee, at that time, there were fears that the disvery would be mised to abort gay babi and wipe gay people off the face of the Earth. ”More like thisAlthough the fears rema, recent years the search for ‘gay gen’ has bee more accepted by the gay muny, no small part bee a blogil explanatn would unrme arguments that beg gay is a social or liftyle choice. For stance, intil tw brothers (siblgs rived om the same fertilised egg) are more likely to both be gay than aternal tws (tws that velop om separate eggs).

STUDY: DNA OF INTIL TWS CAN REVEAL WHO'S GAY

The fact that intil tws have the same DNA and aternal tws share 50 per cent suggts that male homosexualy is gay geneIt was sctisg fay tre to see how homosexualy is hered that led Hamer to the disvery of Xq28. Now chief of the gene stcture and regulatn sectn at the US Natnal Cancer Instute, his study revealed a cur pattern: gay men tend to have more gay uncl and gay male s on their mother’s si of the fay than on their father’s.

GAY MEN TW STUDY

This is bee mal her their X chromosome om their track down the DNA regn lked to the gay tra, Hamer ed a technique lled ‘lkage mappg’, an approach that lets geicists fd a gene even when they don’t know what do or where ’s loted. Lkage mappg works bee close relativ like brothers share not only a particular tra, such as homosexualy, but also the gen unrlyg the tra. So, if you study many pairs of gay brothers and fd a DNA regn that’s the same more than 50 per cent of s, ’s likely to be lked to homosexualy.

A subsequent study 1999 failed to replite Hamer’s rults and other rearchers are sceptil that Xq28 is lked to homosexualy at brothers, immune mothersMany scientists believe that exposure to hormon durg pregnancy heavily fluenc sexualy.

LARGT STUDY OF GAY BROTHERS HOM ON 'GAY GEN'

Durg pre-natal velopment, for example, the sex ans a foet n regnise ttosterone, which will swch on gen to make om a few superficial differenc (among them penis and rg-fger length – both longer homosexuals), gay and straight men’s bodi appear the same. The exceptn is homosexual men’s bras, which show remarkable siari to the bras of heterosexual women, suggtg that sexual orientatn pends on the effect hormon have on the velopg the two factors only go so far explag how homosexualy velops. ”In 1996 Blanchard and Profsor Tony Bogaert revealed a peculiar phenomenon: the more olr brothers a boy has, the greater their chanc of beg homosexual.

”Blanchard believ that homosexualy is “100 per cent blogil”, and timat that the aternal birth orr effect acunts for 15-30 per cent of gay men the populatn. Fertile femalProfsor Andrea Camper Ciani at the Universy of Padova Italy has tted var hypoth by studyg 100 fai of gay men.