2006-02-24 15:22:08文十一
性向取決母親基因
研究發現 「性向」取決母親基因
【2006/02/24 民生報】
同性戀是從娘胎注定的宿命？健康日新聞（HealthDay News）網站21日報導，洛杉磯加州大學的研究人員發現「性向」可能與基因有關：生養多個同性戀兒子的婦女，其基因活動的確與眾不同。
這項研究發現，有超過一個同性戀兒子的婦女當中，將近四分之一的體內X染色體作用相同。作者之一波克蘭表示，研究證實「性向」絕大部份取決於基因，「對一些同性戀男子來說，與X染色體上的基因有關」。這項結果刊登在二月號「人類基因」（Human Genetics）期刊。
波克蘭等人的研究驗證所謂的「X染色體去活性」（X-chromosome inactivation）現象，即女性體內兩個X染色體只有一個是活化的，可表現其帶有的基因；而另一個被去活性，至於何者去活性，則是隨機的結果，機率各是二分之一。波克蘭說：「因此，男女基本上都有一個起作用的X染色體，而男性兼有X和Y染色體，但Y的作用微不足道。」
新研究探討97名有同性戀兒子、以及103名沒有同性戀兒子的婦女，以了解其身體對X染色體的處理方式。波克蘭說，在他們檢驗的細胞中，四分之一的同性戀者媽媽對相同的染色體去活性，這種現象「極不尋常」。相對地，在非同性戀者的媽媽當中，只有4%對上述那個染色體去活性。
研究人員雖不確知研究發現的完整意義，但波克蘭認為他與同僚已對「性向」的起源有更深一層的了解。他說：「這項研究最特別之處，在於發現女性體內有些東西攸關兒子的行為。這是未曾聽聞的新發現。」
Moms’ Genetics Might Help Produce Gay Sons
TUESDAY, Feb. 21 (HealthDay News)
New research adds a twist to the debate on the origins of sexual orientation, suggesting that the genetics of mothers of multiple gay sons act differently than those of other women.
Scientists found that almost one fourth of the mothers who had more than one gay son processed X chromosomes in their bodies in the same way. Normally, women randomly process the chromosomes in one of two ways -- half go one way, half go the other.
The research ”confirms that there is a strong genetic basis for sexual orientation, and that for some gay men, genes on the X chromosome are involved,” said study co-author Sven Bocklandt, a postdoctoral researcher at the University of California at Los Angeles.
The link between genetics and sexual orientation has been a hot topic for more than a decade as a few scientists have tried to find genes that might make people gay or straight. In the new study, Bocklandt and colleagues examined a phenomenon called ”X-chromosome inactivation.”
While females have two X chromosomes, they actually require only one and routinely inactivate the other, Bocklandt said. ”That way, both men and women have basically one functional X chromosome,” he added. Men have both an X and Y chromosome, but the Y chromosome plays a much smaller role, he said.
Women typically inactivate one of their two X chromosomes at random. ”It’s like flipping a coin,” Bocklandt said. ”If you look at a woman in any given (bodily) tissue, you’d expect about half of the cells to inactivate one X, and half would inactivate the other.”
In the new study, researchers looked at 97 mothers of gay sons and 103 mothers without gay sons to see if there was any difference in how they handled their X chromosomes. The findings appear in the February issue of the journal Human Genetics .
”When we looked at women who have gay kids, in those with more than one gay son, we saw a quarter of them inactivate the same X in virtually every cell we checked,” Bocklandt said. ”That’s extremely unusual.”
Forty-four of the women had more than one gay son.
In contrast, 4 percent of mothers with no gay sons activated the chromosome and 13 percent of those with just one gay son did.
The phenomenon of being more likely to inactivate one X chromosome -- known as ”extreme skewing” -- is typically seen only in families that have major genetic irregularities, Bocklandt said.
What does this all mean? The researchers aren’t sure, but Bocklandt thinks he and his colleagues are moving closer to understanding the origins of sexual orientation.
”What’s really remarkable and very novel about this is that you see something in the bodies of women that is linked to a behavioral trait in their sons,” he said. ”That’s new, that’s unheard of.”
Still, there are caveats. Dr. Ionel Sandovici, a genetics researcher at The Babraham Institute in Cambridge, England, pointed out that most of the mothers of multiple gay sons didn’t share the unusual X-chromosome trait. And the study itself is small, which means more research will need to be done to confirm its findings, Sandovici said.
Ultimately, Sandovici added, the origins of sexual orientation remain ”rather a complicated biological puzzle.”
And this line of research does have its critics. Some have worried that, in the future, manipulation of a ”gay gene” or genes might be used as a method of preventing homosexuality in utero , or perhaps even after. But Bocklandt said these kinds of fears shouldn’t stand in the way of legitimate scientific research.
”We’re trying to understand one of the most critical human traits: the ability to love and be attracted to others. Without sexual reproduction we would not exist, and sexual selection played an essential role in evolution,” he said. ”Yet, we have no idea how it works, and that’s what we’re trying to find out. As with any research, the knowledge you acquire could be used for benefit or harm. But if [scientists] would have avoided research because we were afraid of what we were going to find, then we would still be living in the stone age.”
【2006/02/24 民生報】
同性戀是從娘胎注定的宿命？健康日新聞（HealthDay News）網站21日報導，洛杉磯加州大學的研究人員發現「性向」可能與基因有關：生養多個同性戀兒子的婦女，其基因活動的確與眾不同。
這項研究發現，有超過一個同性戀兒子的婦女當中，將近四分之一的體內X染色體作用相同。作者之一波克蘭表示，研究證實「性向」絕大部份取決於基因，「對一些同性戀男子來說，與X染色體上的基因有關」。這項結果刊登在二月號「人類基因」（Human Genetics）期刊。
波克蘭等人的研究驗證所謂的「X染色體去活性」（X-chromosome inactivation）現象，即女性體內兩個X染色體只有一個是活化的，可表現其帶有的基因；而另一個被去活性，至於何者去活性，則是隨機的結果，機率各是二分之一。波克蘭說：「因此，男女基本上都有一個起作用的X染色體，而男性兼有X和Y染色體，但Y的作用微不足道。」
新研究探討97名有同性戀兒子、以及103名沒有同性戀兒子的婦女，以了解其身體對X染色體的處理方式。波克蘭說，在他們檢驗的細胞中，四分之一的同性戀者媽媽對相同的染色體去活性，這種現象「極不尋常」。相對地，在非同性戀者的媽媽當中，只有4%對上述那個染色體去活性。
研究人員雖不確知研究發現的完整意義，但波克蘭認為他與同僚已對「性向」的起源有更深一層的了解。他說：「這項研究最特別之處，在於發現女性體內有些東西攸關兒子的行為。這是未曾聽聞的新發現。」
Moms’ Genetics Might Help Produce Gay Sons
TUESDAY, Feb. 21 (HealthDay News)
New research adds a twist to the debate on the origins of sexual orientation, suggesting that the genetics of mothers of multiple gay sons act differently than those of other women.
Scientists found that almost one fourth of the mothers who had more than one gay son processed X chromosomes in their bodies in the same way. Normally, women randomly process the chromosomes in one of two ways -- half go one way, half go the other.
The research ”confirms that there is a strong genetic basis for sexual orientation, and that for some gay men, genes on the X chromosome are involved,” said study co-author Sven Bocklandt, a postdoctoral researcher at the University of California at Los Angeles.
The link between genetics and sexual orientation has been a hot topic for more than a decade as a few scientists have tried to find genes that might make people gay or straight. In the new study, Bocklandt and colleagues examined a phenomenon called ”X-chromosome inactivation.”
While females have two X chromosomes, they actually require only one and routinely inactivate the other, Bocklandt said. ”That way, both men and women have basically one functional X chromosome,” he added. Men have both an X and Y chromosome, but the Y chromosome plays a much smaller role, he said.
Women typically inactivate one of their two X chromosomes at random. ”It’s like flipping a coin,” Bocklandt said. ”If you look at a woman in any given (bodily) tissue, you’d expect about half of the cells to inactivate one X, and half would inactivate the other.”
In the new study, researchers looked at 97 mothers of gay sons and 103 mothers without gay sons to see if there was any difference in how they handled their X chromosomes. The findings appear in the February issue of the journal Human Genetics .
”When we looked at women who have gay kids, in those with more than one gay son, we saw a quarter of them inactivate the same X in virtually every cell we checked,” Bocklandt said. ”That’s extremely unusual.”
Forty-four of the women had more than one gay son.
In contrast, 4 percent of mothers with no gay sons activated the chromosome and 13 percent of those with just one gay son did.
The phenomenon of being more likely to inactivate one X chromosome -- known as ”extreme skewing” -- is typically seen only in families that have major genetic irregularities, Bocklandt said.
What does this all mean? The researchers aren’t sure, but Bocklandt thinks he and his colleagues are moving closer to understanding the origins of sexual orientation.
”What’s really remarkable and very novel about this is that you see something in the bodies of women that is linked to a behavioral trait in their sons,” he said. ”That’s new, that’s unheard of.”
Still, there are caveats. Dr. Ionel Sandovici, a genetics researcher at The Babraham Institute in Cambridge, England, pointed out that most of the mothers of multiple gay sons didn’t share the unusual X-chromosome trait. And the study itself is small, which means more research will need to be done to confirm its findings, Sandovici said.
Ultimately, Sandovici added, the origins of sexual orientation remain ”rather a complicated biological puzzle.”
And this line of research does have its critics. Some have worried that, in the future, manipulation of a ”gay gene” or genes might be used as a method of preventing homosexuality in utero , or perhaps even after. But Bocklandt said these kinds of fears shouldn’t stand in the way of legitimate scientific research.
”We’re trying to understand one of the most critical human traits: the ability to love and be attracted to others. Without sexual reproduction we would not exist, and sexual selection played an essential role in evolution,” he said. ”Yet, we have no idea how it works, and that’s what we’re trying to find out. As with any research, the knowledge you acquire could be used for benefit or harm. But if [scientists] would have avoided research because we were afraid of what we were going to find, then we would still be living in the stone age.”
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