Researchers are questioning why mutated genes
for breast cancer are not inherited more frequently despite a documented link
with increased fertility in women.
Researchers
from the University of Adelaide are questioning why the mutated genes for
breast and ovarian cancer are not passed on more frequently from one generation
of women to the next.
That’s
despite a documented link between breast cancer genes and increased fertility
in women.
Because
women who carry breast cancer genes are more fertile, in theory they have a
greater chance of passing these genes on to future generations, said Dr. Jack
da Silva from the University’s School of Molecular & Biomedical Science.
“A
recent study in the United States found that mutations in the breast cancer
genes BRCA1 and BRCA2 were directly linked with a 50 percent increase in the
fertility of women, which is a huge number,” said da Silva.
“With
such an increased fertility rate, you would expect to see a high frequency of
these cancer-causing genes in modern populations, but in fact that is not the
case – the frequencies are relatively low,” he added.
In a
paper published in the Proceedings of the Royal Society B, he
argues that the so-called “grandmother effect” may in part be the reason behind
this phenomenon.
In an
earlier study, researchers found that post-menopausal women create a
“grandmother effect” – that is, the longer they live, the more they are able to
support their daughters and their grandchildren, thereby creating an
environment in which more grandchildren are born.
The
reverse of this is that women who die earlier – such as from breast or ovarian
cancer, which are usually post-menopausal – will no longer be able to support
their daughters and grandchildren. This has the effect of limiting the number
of grandchildren born, and therefore the chances of passing on the mutated
genes to the next generation, da Silva explained.
However,
the “grandmother effect” does not entirely negate the increased fertility
caused by breast cancer genes, he said.
“Our
change to today’s industrial and technological age has been relatively rapid in
human history. For most of our existence, we have been hunter-gatherers. During
this time, female fertility was limited, and this may have reduced the increase
in fertility caused by mutations of these genes,” he said.
Da
Silva says further studies examining modern-day hunter-gatherer societies might
shed more light on how and why the spread of these genetic mutations occurs
across generations.
The
article can be found at: da Silva J et al. (2012)
BRCA1/2 mutations, fertility and the grandmother effect.
Source: University of Adelaide.
No comments:
Post a Comment