Men’s mental development can be held back by a genetic defects on the female X-chromosone, a study has revealed.
The international study by 70 researchers of families affected by genetic learning disabilities around the world concluded that intellectual impairment is caused when nine specific genes on the female X-chromosome go wrong.
Men are more likely to be affected than women because they only have one X-chromosome, paired with a male Y-chromosome. Women have two X-chromosomes, so the harmful effects of one can be counteracted if the other is functioning normally.
The scientists, whose findings are reported online in the journal Nature Genetics, also found that missing 1% to 2% of X-genes does a person no harm.
Researcher Professor Mike Stratton, from the Wellcome Trust Sanger Institute in Hinxton, Cambridgeshire, said: ‘It is remarkable that so many protein-coding genes can be lost without any apparent effect on an individual’s normal existence.’
Dr Lucy Raymond, reader in Neurogenetics at the Cambridge Institute for Medical Research at Cambridge University, added: ‘We already offer genetic counselling to families with X-linked learning disabilities.
‘This new research uncovers yet more genes that can be incorporated to improve the provision of diagnostics to families with learning disabilities and allow us to develop more comprehensive genetic counselling in the future.’