[Rushtalk] Scientists find DNA differences between gay men and their straight twin brothers

Stephen A. Frye s.frye at verizon.net
Mon Nov 9 19:35:59 MST 2015

Of course you think it's a fraud.  If it turns out to be anything other than
100% free choice, it hurts our whole perspective.


Science be damned - full speed ahead!


From: rushtalk-bounces at csdco.com [mailto:rushtalk-bounces at csdco.com] On
Behalf Of John A. Quayle
Sent: Monday, November 09, 2015 4:50 PM
To: Rushtalk Discussion List; Rushtalk
Subject: Re: [Rushtalk] Scientists find DNA differences between gay men and
their straight twin brothers


         IF this is true (and I'm thinking it's a complete fraud), the God's
got some apologizing to do those who lived in ancient Sodom and
Gomorrah.................    - jaq

At 03:25 PM 11/8/2015, Carl Spitzer wrote:


Scientists find DNA differences between gay men and their straight twin

 Homosexuality epigenome markers
nature-nurture-001/750/750x422>  Could the molecular signals that turn genes
on and off reveal a person's sexual orientation? New research identifies
epigenomic "marks" linked to homosexuality. But experts say the origins of
partner preference remain a mystery.

(Chuck Nigash ,Stephen Sedam / Los Angeles Times)  Melissa Healy
Melissa Healy
For men, new research suggests that clues to sexual orientation may lie not
just in the genes, but in the spaces between the DNA, where molecular marks
instruct genes when to turn on and off and how strongly to express

On Thursday, UCLA molecular biologist Tuck C. Ngun
reported that in studying the genetic material of 47 pairs of identical male
twins, he has identified "epigenetic marks" in nine areas of the human
genome that are strongly linked to male homosexuality.

In individuals, said Ngun, the presence of these distinct molecular marks
can predict homosexuality with an accuracy of close to 70%.

That news, presented at the 2015 meeting of the American Society of Human
Genetics on Thursday, may leave the genetically uninitiated scratching their

But experts said the results -- as yet unpublished in a peer-reviewed
journal -- offer preliminary new evidence that a man's genetic inheritance
is only one influence on his sexual orientation. Through the epigenome, the
results suggest, some facet of life experience likely also primes a man for
same-sex attraction.

urasia-20151008-story.html> DNA from 4,500-year-old Ethiopian reveals
surprise about ancest  DNA from 4,500-year-old Ethiopian reveals surprise
about ancestry of Africans
urasia-20151008-story.html>  Over a person's lifetime, myriad environmental
factors -- nutrition, poverty, a mother's love, education, exposure to toxic
chemicals -- all help shape the person he will become.

Researchers working in the young science of epigenetics acknowledge they are
unsure just how an individual's epigenome is formed. But they increasingly
suspect it is forged, in part, by the stresses and demands of external
influences. A set of chemical marks that lies between the genes, the
epigenome changes the function of genetic material, turning the human body's
roughly 20,000 protein-coding genes on or off in response to the needs of
the moment.

While genes rarely change over a lifetime, the epigenome is constantly

Geneticists suggest that together, the human genome and its epigenome
reflect the interaction of nature and nurture -- both our fixed inheritance
and our bodies' flexible responses to the world -- in making us who we are.

Ngun's study of twins doesn't reveal how or when a male takes on the
epigenomic marks that distinguish him as homosexual. Many researchers
believe that a person's eventual sexual preferences are shaped in the uterus
<http://articles.latimes.com/2006/jun/27/science/sci-brothers27> , by
hormonal shifts during key stages of fetal brain development.

FROM THE ARCHIVES: A closer look at scientific inquiry into sexual
orientation <http://articles.latimes.com/2001/may/21/health/he-533> 

By imprinting themselves on the epigenome, though, environmental influences
may powerfully affect how an individual's genes express themselves over the
course of his life. Ngun's findings suggest they may interact with genes to
nudge sexual orientation in one direction or the other.

"The relative contributions of biology versus culture and experience in
shaping sexual orientation in humans continues to be debated," said
University of Maryland pharmacology professor Margaret M. McCarthy, who was
not involved in the current study. "But regardless of when, or even how,
these epigenetic changes occur," she added, the new research "demonstrates a
biological basis to partner preference."

To find the epigenomic markers of male homosexuality, Ngun, a postdoctoral
researcher at UCLA's Geffen School of Medicine, combed through the genetic
material of 47 sets of identical male twins. Thirty-seven of those twin sets
were pairs in which one was homosexual and the other was heterosexual. In 10
of the pairs studied, both twins identified as homosexual.

In identical twins, DNA is shared and overlaps perfectly. But the existence
of twin pairs in which one is homosexual and the other is not offers strong
evidence that something other than DNA alone influences sexual orientation.
Ngun and his colleagues looked for patterns of DNA methylation -- the
chemical process by which the epigenome is encoded -- to identify the
missing factor in partner preference.

Their analysis generated a dataset far too large for a team of humans to
make sense of. So they unleashed a machine learning algorithm on the data to
search for regularities that distinguished the epigenomes of homosexual
twin-pairs from twins in which only one was homosexual.

In nine compact regions scattered across the genome, they found patterns of
epigenomic differences that would allow a prediction far more accurate than
a random guess of an individual's sexual orientation, Ngun reported

McCarthy and other experts cautioned that the discovery of epigenomic marks
suggestive of homosexuality is a far cry from finding the causes of sexual

The distinctive epigenomic marks observed by Ngun and his colleagues could
result from some other biological or lifestyle factor common to homosexual
men but unrelated to their sexuality, said University of Utah geneticist
Christopher Gregg. They could correlate with homosexuality but have nothing
to do with it.

"Epigenetic marks are the consequence of complex interactions between the
genetics, development and environment of an individual," said University of
Cambridge geneticist Eric Miska. "Simple correlations -- if significant --
of epigenetic marks of an individual with anything from favorite football
player to disease risk does not imply a causal relationship or

One longtime researcher in the field of sexual orientation praised Ngun's
use of identical twins as a means of teasing apart the various biological
factors that influence the trait.

"Our best guess is that there are genes" that affect a man's sexual
orientation "because that's what twin studies suggest," said Northwestern
University psychologist J. Michael Bailey, who  has explored a range of
physiological markers that point to homosexuality's origins in the womb. But
the existence of identical twin pairs in which only one is homosexual
"conclusively suggest that genes don't explain everything," Bailey added.

While Ngun's research needs to be replicated in larger studies of twins, it
advances the fitful process of better understanding how - and when - a boy's
sexual orientation develops, Bailey said.

Follow me on Twitter @LATMelissaHealy <https://twitter.com/LATMelissaHealy>
and "like" Los Angeles Times Science
<https://www.facebook.com/latimesscience> & Health on Facebook.


So why not test for it and adjust insurance premiums according to risk??
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