THERE has been much debate over “gay genes”. Now an intriguing study raises another possibility: in some cases, variations in the genetic program we inherit from our parents, rather than in the genes themselves, might determine sexual preference.
Our genome is “programmed” by the addition of chemical markers called methyl groups to the DNA, which shut down genes. One of the most dramatic examples of methylation is the shutdown of one of the two X chromosomes (one from each parent) in every woman’s cells, a process called X-inactivation (New Scientist, 10 May 2003, p 42).
Normally, this process is…
