Heredity and Genetic Testing for Autism

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Is autism really a genetic disorder created, in part, as a result of older parents? A large-scale research study conducted by a team based at Cold Spring Harbor Laboratory (CSHL) in Long Island, N.Y says, yes, perhaps.

Root Cause of Autism 

According to the team's study, a combination of heredity and spontaneous genetic mutation is at the root of most cases of autism. Most interestingly (and, perhaps, disturbingly), those genetic mutations may be the outcome of a societal trend toward having children later in life.

In addition, some mothers, say the researchers, may carry an autism gene which does not show its effects until it is passed down — usually to a male child.

This is a complex set of findings, and hard to digest without further explanation. Kenny Ye, one of the primary researchers on the project, kindly agreed to provide a layperson's description of the team's finding:

To clarify.., we estimate that majority of autism cases (about 2/3, or, conservatively 50%) are caused by new mutation (that is not in parents' genome but happened in sperm and eggs). There could be many risk factors for such mutation, including parental age, environmental exposure, life style etc. I do believe that the increasing parental age is behind the increase of autism. And important future research is to identify other risk factors.

The minority of autism cases (about 1/3) are caused by mutations inherited from one of the parents (we hypothesize mostly from the mother). Offspring have a 50% chance inheriting it.... The parent (likely the mother) [would have] acquired such mutations but [would not] show severe symptoms.

With further research, Ye believes, it may be possible to create a genetic test for autism within about five years.

"Because of the uncertainty of the outcome," he says, "I don't think that it should be used for prenatal testing as for Down syndrome, but rather as a tool for starting early intervention."