Seattle ? The gene sets of a four-member family were analyzed in research that suggested parents pass fewer gene mutations than thought to their offspring.

Scanning the genomes of the family enabled the research team to pinpoint the mutations that caused two rare diseases in their children, according to a study in the journal Science. By comparing the DNA sequences of all four family members, the authors found that each parent gave 30 mutations, for a total of 60, to their children, the researchers said in a statement.

Previous studies had estimated that each parent passes 75 gene mutations to their children, with many of those not having any consequence. Understanding how parents pass mutations to their children may help narrow the search for genetic causes of diseases, said the research team headed by David Galas and Leroy Hood at the Institute for Systems Biology in Seattle.