The largest-ever study on autism genes found most siblings struggling with the disorder possess different genetic risk factors.

The study's data became part of an upload of over 1,000 autism genomes to the Autism Speaks MSSNG portal in Google Cloud Platform, which will be available for public research, Autism Speaks reported.

"This is a historic day," said study leader Stephen Scherer, "as it marks the first time whole genome sequences for autism will be available for research on the MSSNG open-science database. This is an exemplar for a future when open-access genomics will lead to personalized treatments for many developmental and medical disorders."

In the study the researchers sequenced 340 whole genomes from 85 families, each with two children affected by autism. They found 69 percent of the siblings had little to no overlap in gene variations linked to autism. These findings dispute long-held beliefs that siblings with the disorder inherit the same autism-predisposing genes from their parents.

The findings could help researchers find answers as to why certain children develop autism and even provide insight into related medical conditions.

"We knew that there were many differences in autism, but our recent findings firmly nail that down. We believe that each child with autism is like a snowflake - unique from the other. This means we should not be looking just for suspected autism-risk genes, as is typically done in diagnostic genetic testing," Scherer said. "A full assessment of each individual's genome is needed to determine how to best use knowledge of genetic factors in personalized autism treatment." Whole genome sequencing goes far beyond traditional genetic testing to analyze an individual's complete DNA sequence.

The findings were reported in a recent edition of the journal Nature Medicine.