From Steve Tash
Your article on explaining autism’s capriciousness seems to yell out that the condition is sex-linked and on the X chromosome (28 July, p 18).
If men, who inherit only one of their mother’s X chromosomes, have a 50 per cent chance of inheriting it, while the odds are much lower for women, who have two X chromosomes, does this not suggest autism is caused by a recessive gene or genes and only appears dominant in men because they don’t have a second X chromosome?
The editor writes:
• The X chromosome may indeed be involved in some cases of autism inheritance, but statistical analysis revealed that it cannot explain most cases. In a true X-linked disease, you would expect affected brothers to have inherited the same one of their mother’s two X chromosomes, the faulty one. But in families with several autistic boys, these brothers often don’t share the same X chromosome, suggesting that other chromosomes must be involved.
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