Scientists at the University of California, San Francisco, in the United States, have announced a breakthrough that may be crucial in explaining female longevity.
Throughout the world, women live longer than men, a trend that is not unique to humans, as it is also found in most animal species.
Now the researchers say that the cause of this phenomenon may be the important role played by the second X chromosome present in mammals. This chromosome contains many genes related to the brain and is essential for survival: without at least an X, an animal can not live.
In turn, the Y chromosome, present only in males, is not necessary for survival and contains very few genes other than those that create secondary sexual characteristics such as male genitalia and facial hair.
In their experiment, the team modified the chromosomal combinations in mice. In addition to the combinations found in nature – women with XX chromosomes with ovaries and males with XY with testicles – created two laboratory combinations: males with XX chromosomes with testes and females with XY chromosomes with ovaries.
Rats were genetically identical, except for the sex chromosomes, and grew in the same environment. Likewise, those who had two X chromosomes lived longer than those who had an X chromosome and a Y chromosome.
Rats that had a combination of XX chromosomes and ovaries were the ones that lived the most. On the other hand, the XX combination in males with testicles protected the animals from premature death, but without prolonging their life beyond normal expectation.
"Those who had the XX combination escaped premature death"
"For a longer lifespan, mice needed to have ovaries and XX chromosomes," said Iryna Lobach, a co-author of the study. "But in terms of living a normal life, it did not matter if they had ovaries or testicles, those who had the XX combination escaped premature death during aging," said the researcher.
The study required several years because the rats were observed for 30 months, during which time they died or survived. The benefits of having two X chromosomes began to be reflected when the animals were 23 months or older. (Source: RT)