Researchers have determined that there are hundreds of biological
differences between the sexes when it comes to gene expression in the
cerebral cortex of humans and other primates. These findings,
published June 20th in the open-access journal PLoS Genetics, indicate
that some of these differences arose a very long time ago and have
been preserved through evolution. These conserved differences
constitute a signature of sex differences in the brain.

Many more obvious gender differences have been preserved throughout
primate evolution; examples include average body size and weight, and
genitalia design. This study, believed to be the first of its kind,
focuses on gene expression within the cerebral cortex. The cerebral
cortex is involved in many of the more complex functions in both
humans and other primates, including memory, attentiveness, thought
processes and language.

The researchers measured gene expression in the brains of male and
female primates from three species: humans, macaques, and marmosets.
To measure activity of specific genes, the products of genes (RNA)
obtained from the brain of each animal were hybridized to microarrays
containing thousands of DNA clones coding for thousands of genes. The
authors also investigated DNA sequence differences among primates for
genes showing different levels of expression between the sexes.

"Knowledge about gender differences is important for many reasons. For
example, this information may be used in the future to calculate
medical dosages, as well as for other treatments of diseases or damage
to the brain," says team leader Professor Elena Jazin, at Uppsala
University, Sweden.

In addition to the results mentioned above, the researchers also
report on evolutionary speeds in genes that have been identified as
male or female-oriented. This could provide clues about the power of
natural selection processes during the evolution of primates.

Lead author Björn Reinius notes that the study does not determine
whether these differences in gene expression are in any way
functionally significant. Such questions remain to be answered by
future studies.

Source: Uppsala University
http://www.physorg.com/news133147403.html