For years, the scientific community has tried to clarify why females live longer than males in most animal species. Countless biological and psychosocial factors have been considered. Although to date this is a statistically proven fact, the reasons why this happens are still unknown.
A study conducted at the University of California-San Francisco has just thrown data that puts the focus on the second X chromosome, which could reveal itself as the great secret of longevity and the reason why women live longer.
This research puts on the table the importance of the X chromosomes, without which life is not possible. Unlike the Y chromosomes, which contain very few different genes and are limited to creating physical characteristics, such as the male genitals or facial hair, but are not necessary for survival. Thus, this factor could begin to explain why life expectancy is higher in women.
That women live longer seems to be related to the second X chromosome.
The lead author of the study is a professor of neurology at the University of California-San Francisco, Dena Dubal. The results were published in the scientific journal Aging Cell. The research has been carried out in a group of experimental mice created in the laboratory.
The mice were created genetically identical, except for their sex chromosomes. It was made on four different groups. The first and second group consisted of XX mice with ovaries and XY with testicles. The third and fourth groups were artificially created as XX with testicles and XY with ovaries.
The study has shown that mice carrying the double X chromosome lived longer than the XY carriers, regardless of whether they had ovaries or testicles. They also found that, of all the XX carriers, the longest were the ones with ovaries.
They lived well beyond average age in mice. That is, the longest combination was the mice with ovaries and double X chromosome, the same created by the natural order.
These were followed by XX mice with testes, which did not survive much longer than the average life of a mouse.
Both survived all carriers of XY chromosomes. The life expectancy in mice bearing double chromosome XX with ovaries reached 30 months, when the average of an XY mouse does not usually exceed 12 months of life.
“For a longer lifespan, mice need to have ovaries with two XX chromosomes, according to the natural order.”
Summarized Iryna Lobach, assistant professor of epidemiology and biostatistics at UCSF and co-author of the report.
Women live longer thanks to the genetic mechanism of the X chromosome.
The X chromosome, carried by both women and men, is crucial for survival. It contains many genes related to the brain. In addition, the presence of pathological recessive mutations in a gene of the X microsome makes males more vulnerable to suffer the inherited pathology. For a female to develop a recessive pathology in a microsome X gene, two copies with a pathological mutation are necessary, while in males only one copy is necessary.
It seems that on an X chromosome there are six times more genes related to intelligence than the rest of the chromosome. In this way, if a gene fails, this deficiency is replaced by the second X chromosome, while in man this substitution is not possible.
Previous studies conducted by Dr. Dubal and argued that this could explain why there is between 30% and 50% more intellectual disabilities among men. Gillian Turner and Michael Partington, from the Children’s Prince of Wales Hospitals in Sydney and the Newcastle Suburbs of Newcastle, both in Australia, recently came to this conclusion.