Grandmothers saved us from breast cancer
Why didn't the breast cancer mutation spread to all women?
Kirill Stasevich, Compulenta
Mutations that cause breast cancer increase fertility, but at the same time mortality is also increasing among the older generation of women who could take care of grandchildren.
Breast cancer is one of the most common types of cancer. Like other tumors, it can occur due to mutations in certain genes. But a year ago, American researchers discovered a curious thing: in humans, mutations in the "cancer-forming" genes BRCA1 or BRCA2 are accompanied by an increase in fertility. That is, the more likely a woman is to get breast cancer, the more children she has.
The influence of these genes on fertility is so great that already in the fourth generation almost every woman would have a dangerous variant of the gene in the genome. However, this mutation is not so common at all. In an article published in the journal Proceedings of the Royal Society B (BRCA1/2 mutations, fertility and the grandmother effect), geneticist Jack da Silva from the University of Adelaide (Australia) explains this by saying that the genes BRCA1 and BRCA2, increasing fertility, simultaneously have a bad effect on the care of offspring. Most women with these genes get a tumor after menopause. They can no longer give birth to their children, but they are able to take care of their grandchildren. However, with the BRCA1 and BRCA2 genes, the probability of dying in 50-60 years increases greatly, and there can be no grandmother's care.
According to the scientist, the care of offspring by older ancestors was more than relevant at the dawn of mankind, when people were mainly engaged in hunting. While the relatively young individuals were hunting, the older ones were watching their children. Obviously, in the absence of the grandmother, the child had less chance to survive – which means that the cancer mutation was less likely to pass into the next generation.
The link between the BRCA1 and BRCA2 genes and fertility can be traced back to the 30s of the last century: women with cancerous gene variants had on average 50% more children. Further, however, it becomes difficult to trace this interdependence, as well as the "grandmother effect" due to the widespread use of contraceptives and sociocultural changes in general. According to Mr. da Silva, the current spread of the mutation is due to the fact that since some time a person has ceased to depend on hunting, but has not yet learned how to effectively protect himself during sex. During this period, the mutation could dramatically increase its frequency in the population, although it could not completely capture the female population of the planet.
The molecular reasons why the probability of breast cancer is associated with fertility are still unknown. Researchers partly sin on telomeres – the end sections of chromosomes that determine the life span of a cell. Mutations in BRCA1/2 can lengthen telomeres, while long tails of chromosomes are often the cause of cancer. But how long telomeres can affect the number of children, scientists cannot yet say.
Prepared based on the materials of the University of Adelaide: Mystery of the missing breast cancer genes.
Portal "Eternal youth" http://vechnayamolodost.ru11.05.2012