o The Frog Blog: Biology Prize Entries 2011 - Genetics & Homosexuality

Friday, 11 March 2011

Biology Prize Entries 2011 - Genetics & Homosexuality

Boston University psychiatrist Richard Pillard is gay. Not only that; he has a gay brother, a lesbian sister, and a bisexual daughter. And his father was. Pillard found out when he read his father’s diaries after his death- was in a sexual relationship with another man early in his adult life. This personal history was Pillard’s motivation to investigate whether homosexuality generally runs in families, a line of research he began in the early 1980’s.

The first and perhaps the most influential of a number of studies Pillard compiled over his career was the Twin Studies, published throughout the early 1990’s. In this study, Pillard and his colleagues gathered twins from all walks of life and collected statistics based on the sexual orientation of each set of twins. His results were astounding, as of a set of monozygotic twins where one was a homosexual, the other was also homosexual roughly 50% of the time-with the results being directly proportionate yet significantly less in dizygotic twins.

The results of Pillard’s study reverberated throughout the scientific community yet were inconclusive and ambiguous; thus fueling other scientists to investigate into an area of study that could potentially change the fundamental core of society, and challenge our morals. One particular scientist who heard the calling was Dean Hamer of Johns Hopkins University, who in 1998 published a report which gave increasing, if not conclusive, validity to Pillard’s original assertion.

Taking a more scientific approach, Hamer scanned specific genes which he believed could be the root of a homosexual pre-disposition-but to no avail. He then attempted another approach where which he scanned large sections of the genome, or the entire genome, without any preconceived ideas as to which genes might be involved. Hamer started by recruiting a sample of gay men and asked about the sexual orientation of their relatives-immediate or otherwise. As anticipated, Hamer found abnormally high rates of homosexuality among the brothers, uncles, and male cousins of the index cases. However, of the two kinds of uncles (maternal and paternal), only maternal uncles had significantly increased rates, and of the four types of male first cousins, (sons of maternal aunts, sons of maternal uncles, sons of paternal aunts, sons of paternal uncles), only the sons of maternal aunts had these same significant increases. In other words, only men connected to the index cases through the female line had an increased chance of being gay. To Hamer, this pattern suggested that there might be maternal inheritance of genes predisposing of male homosexuality. Hamer therefore focused his molecular studies on the X chromosome.

For the X chromosome study, Hamer and his colleagues recruited 40 pairs of brothers, each pair consisting of two gay men. Because of the phenomenon called crossing over, in which two maternal X chromosomes break up and rejoin during the development of the ovum, only the region of the X chromosome near to the initially proposed “gay gene” will be co-inherited by the brothers at an above –chance rate. Hamer therefore examined 22 DNA markers- sights where DNA sequences are known to vary among individuals in the population – that are scattered along the X chromosome. In Hamer’s data, the pairs of brothers shared the same markers at an above chance rate in just region of the X chromosome, a region named Xq28, which lies near the tip of the long arm of the chromosome. Despite further testing pending, Hamer’s results have been widely interpreted to confirm a certain genetic pre-disposition to homosexuality. Despite this, 1/3rd of Americans still believe it is a “lifestyle choice”, while only around 1/5th believes it is “out of their control.

Considering the political and social impact of such an issue, and especially in light of Proposition 8 in California, I believe this topic has considerable social and scientific importance, not only in the way we view homosexuals, but also in the way that we view ourselves in light of such a substantial discovery.

Patrick McGonagle, Form VI (Patrick hails from California, hence the American angle taken at the end).

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