Mutations in certain genes contribute specifically to autism, and others only to developmental delay.

The number of top autism genes has risen from 65 to 99, based on an analysis of nearly 35,000 sequences. And researchers are seeing the first hints of autism risk variants in the regions between genes.

Genetic variants that affect mitochondria, the organelles that power cells, may increase the risk of autism.

A single gene, OTUD7A, may account for most of the features seen in people missing a segment of chromosome 15 known as 15q13.3.

People with attention deficit hyperactivity disorder may carry certain rare, harmful mutations in many of the same genes as people with autism.

A cannabis gel may ease features of fragile X syndrome, omega fatty acids show promise for autism in two trials, and oxytocin reinforces social behaviors through the brain’s reward pathway.

Mutations that appear in only some of the body’s cells contribute to autism in about 4 percent of people with the condition.

Scientists this week announced the release of nearly 7,000 whole-genome sequences from a collection of families that each have one child with autism.

People with autism aren’t easily surprised, the social camouflage some girls and women with autism use may preclude diagnosis, and autism-related genes are rooted deep in human ancestry.