The genetic link to male homosexuality has come under scrutiny. A team of researchers at the US National Cancer Institute had earlier studied 40 pairs of gay brothers from families with maternal gay relatives. They observed that the brothers conspicuously shared certain DNA markers on a region of the X chromosome, which males inherit only from their mothers. The researchers concluded that this chromosomal segment contained a gene that could drive males toward homosexuality. This has been challenged by clinical neurologists George Rice and George Ebers at the University of Western Ontario, in London, Canada. The team undertook their own study on 52 pairs of gay brothers and found that they were no more likely to share the particular gene than would be expected by chance. ( Science , Vol 284, No 5414).