X chromosome not the reason for sex differences in lifespan

phys.org | 2/13/2018 | Staff
vpp1219 (Posted by) Level 3
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The shorter average lifespan of males compared to females appears not to be a result of the fact that males have only one X chromosome. This is the conclusion from a research study on fruit flies at Linköping University, Sweden. The results have been published in the scientific journal Evolution.

It is common that the lifespans of males and females differ. For mammals, including humans, females live on average somewhat longer than males. The difference in humans at a global level is that women live 4.7 years longer than men, according to statistics from WHO for 2015. We do not know why this is the case in so many species, but several theories have been put forward. Researchers at Linköping University (LiU) have now had a close look at one of the theories concerning the role of genetics in sex differences in lifespan.

Difference - Sexes - Numbers - Sex - Chromosomes

One obvious genetic difference between the sexes is that they have different numbers of sex chromosomes, and what is known as the "unguarded X hypothesis" is based on this. In many species, including humans, females have two X chromosomes while males have an X and a Y chromosome. In birds, and in some species of fish, reptiles and insects, males have two copies of the same sex chromosome, and in such cases it is most often males who have the longer lifespan.

The sex that has two X chromosomes has two variants of each gene on the X chromosome. The gene variants act as back-ups for each other, so if a gene on the X chromosome is not functional, the gene copy on the other chromosome can compensate for this. In the sex that has two different sex chromosomes (one X and one Y), in contrast, only one copy of most genes on the X chromosome is present, and no...
(Excerpt) Read more at: phys.org
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