Washington, Feb 3 (IANS) Men and women tend to behave differently, especially when it comes to sex and parenting, thanks to the role their genes and sex hormones play.

New evidence shows that the sex hormones - testosterone, estrogen, and progesterone - act in a key region of the brain, switching certain genes on and others off.

When researchers tinkered with each of these genes one by one, animals showed subtle but important shifts in gender-specific behaviours, such as how males mate or females care for their pups, the journal Cell reports.

“What this means is that complex behaviours like male mating or maternal care in mice can be deconstructed at the genetic level,” said Nirao Shah of the University of California, San Francisco.

Researchers focused specifically on the hypothalamus, a brain region governing sex-specific behaviours. They singled out 16 genes with clear sex differences in distinct neurons (brain cells) in the hypothalamus, according to a California statement.

Surprisingly, Shah’s team found that many of these genes also show sex differences in the amygdala, a part of the brain important for emotions.

Mice missing only one of these 16 genes seemed to behave normally. But upon closer observation, these mice showed significant differences in sex-specific behaviours.

For instance, Shah, who led the study, explained, females mutant for one gene took longer to return their pups to the nest and to fight off intruders. “They still take care of their pups, but less effectively,” he said.

In other experiments, deletion of a single gene produced females that were two-fold less receptive to mating with males. Similarly, males mutant for another gene were less interested in females.