Surprisingly, the females in the sample had more CNVs than the males. Although both sexes in the study had neurodevelopmental disorders, the females were carrying a bigger "burden" of genetic damage.
Eichler says this fits with females somehow being better protected from the effects of the CNVs. "It takes a lot more mutational hits to make a woman cross the threshold for a disorder," he said.
"The next question was... do you see this in autism?" said Eichler.
The team then focused on autism alone using a separate group of 762 families with autism spectrum disorders. The females in this group carried an even greater burden of CNVs.
These women were also more likely to carry tiny harmful mutations, affecting just a couple of base pairs in the DNA, than the men in the group.
Why are males more vulnerable?
Eichler now wants to do more research on thousands rather than hundreds of people with autism spectrum disorder, to validate and extend the results. He'd like to pinpoint the genes that most put people at risk of the disease.