Here's a cheerful finding
for those who say that males push females around too much: On
the molecular level, it appears male genes may have to leave
their homes for protection, researchers report.
"Home" is the X
chromosome, which plays a key role in determining the sex of
the carrier. A female has two X chromosomes, while a male has
one X and one much smaller Y chromosome. Studies in mice and
humans show an unusually large number of genes can jump from
the X chromosome to non-sex chromosomes, a research team at
the University of Chicago reports in the Jan. 23 issue of Science.
That finding contradicts
two beliefs widely held by geneticists, explains study leader
Manyuan Long, an associate professor of ecology and evolution.
It has been thought
that gene traffic is no greater for the X chromosome than for
all the other genes, which are called autosomes. "That's just
not true," Long says.
And standard theory
holds that the X chromosome is the site of action for most sex-related
genes. The Chicago studies show that many of the genes that
leave the X chromosome are involved in male sexual development,
and they may go elsewhere to do what they have to do.
At the moment, this
is an exercise in pure, basic science. But it might someday
provide useful insights into treatment of male sexual problems,
since many of the jumping genes are involved in sperm formation,
says J.J. Emerson, a member of the research team.
"This helps us understand
which particular genes are likely to be involved in spermatogenesis,"
Emerson says. "So we can infer that anyone looking for genes
involved with sperm formation can look at our genes."
As every schoolboy
knows, chromosomes carry the genes that carry the information
for production of the proteins that enable a living organism
to live and grow.
Growth means the
production of new cells, and therefore of new chromosomes. A
human, for example, starts as a single cell, which divides to
form two cells, which divide to form four, and so on. At each
division, a complete set of chromosomes is produced for each
new cell.
But the chromosomal
production line is not perfect. Changes occur -- changes that
can result in the new traits that are essential for the evolution
of life. And those changes can include the transfer of a gene
from one chromosome to another.
"What we see is
that when genes are copied from one chromosome to another, the
copying from the X chromosome is excessive," Emerson says. "The
explanation is that natural selection is responsible for this
excess."
There are two possible
reasons why this occurs, he says, and both of them are based
on the weakness of males -- at least at the genetic level.
One is that a male
carries only a single X chromosome, and therefore it is less
likely that a male-helpful gene will be able to do its work.
By jumping to an autosome, the male gene increases its chances
of being productive.
"The other explanation
is sexual antagonism," Emerson says. "We would expect that female
genes would have more of a say on the X chromosome. If so, and
they don't care about male genes, in those cases where it would
benefit females at the expense of males the only way for a male
gene to work is to escape from the X chromosome."
If that explanation
is correct, the war between men and women is being waged molecule
against molecule. And at that level, it is the male who is weakest.
More information
A basic guide to
genetics can be found at the National
Library of Medicine or the National
Human Genome Research Institute.
Reference
Source 101
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