An excellent blog from the other side of the world. Very much worth a read. In this particular post the mother of an autistic lad has been reading Simon Baron Cohen and then relfects that there’s a great deal of similarity between his theoretical descriptions and their personality types.

One thing though:

Another concern about buying into Mr. Baron Cohen’s hypothesis is that if the cause is purely due to genes, then this means other children of the same parents will be autistic too, which is not necessarily the case. Yes, there is a higher chance of them being autistic too but it is definitely not definite. Alhamdulillah, my 19 month old Alisha seems neurotypical to me, talking and playing in accordance with the milestones of typical children.

That’s not quite how genetics works. Take something that we know is absolutely genetically determined, like cystic fibrosis. Even if both parents are carriers the chance of any individual child actually having cystic fibrosis is one in four.

Think of it this way. There’s one specific variation of a gene which leads to cystic fibrosis. And you get a pair of genes, one from each parent, for each gene. To have the actual disease, rather than simply be a carrier, both copies of the gene must be the cystic fibrosis types. OK, now, the parents are both carriers but not suffering from the disease. So their copies of the genes are gene (cf) and gene (not cf). Yes? And you inherit one copy of each gene from each parent, yes?

So the possible combinations in any child are gene (cf) gene (cf), gene (cf) gene (not cf), gene (not cf) gene (cf) and gene (not cf) gene (not cf).

Four possible combinations and only one means that the child suffers from cystic fibrosis (where it is gene (cf) gene (cf)), two that it is a carrier and one that it is entirely free of it.

This is true of any recessive gene.

Now, we’re also pretty sure that there is no one gene for autism, rather, that there’s a combination that cause it. That reduces the chances again: say that it’s two genes and everything is the same as before. Instead of there being four possible genetic combinations, there will be 8, and the chance of any one child being autistic will be one in 8. If there’s three then the number goes up again…to 24, and thus a one in 24 chance.

Actually, you can try and run this back the other way. We know that if one child is autistic then the chances of a second being so rise from those of the general population. But if we can work out how much higher, then we might be able to see how many genes are interacting.