There has been a significant body of progress establishing the biological basis of sexual orientation. People fixate on the idea of a silver bullet gene that could be switched on and off, but in the research several genes are implicated, genes are pleiotropic, the role of epigenetic factors is just beginning to be explored, and we know that in utero hormone levels affect sexual orientation also.
Here's the Guardian:
Male sexual orientation influenced by genes, study shows
A study of gay men in the US has found fresh evidence that male sexual orientation is influenced by genes. Scientists tested the DNA of 400 gay men and found that genes on at least two chromosomes affected whether a man was gay or straight.
A region of the X chromosome called Xq28 had some impact on men's sexual behaviour though scientists have no idea which of the many genes in the region are involved, nor how many lie elsewhere in the genome.
Another stretch of DNA on chromosome 8 also played a role in male sexual orientation though again the precise mechanism is unclear.
Researchers have speculated in the past that genes linked to homosexuality in men may have survived evolution because they happened to make women who carried them more fertile. This may be the case for genes in the Xq28 region, as the X chromosome is passed down to men exclusively from their mothers.
It's settled science that organic sexual attraction is biologically based, all that is happening now is running down the specific factors at play. I love science.
I found this question neatly turned to the more pressing issue:
Rahman [a psychologist at King's College London] rejected the idea that genetics research could be used to discriminate against people on the basis of their sexual orientation. "I don't see how genetics would contribute more to the persecution, discrimination and stigmatisation of lesbian, gay, bisexual and transgender people any more than social, cultural or learning explanations. Historically, the persecution and awful treatment of LGBT groups has been because politicians, religious leaders and societies have viewed sexual orientation as 'choice' or due to poor upbringing."
Steven Rose, of the Open University, said: "What worries me is not the extent, if at all, to which our genetic, epigenetic or neural constitution and development affect our sexual preferences, but the huge moral panic and religious and political agenda which surrounds the question."