Tuesday, September 18, 2012
DNA evidence as to why women live longer than men
Towards the beginning of August, geneticists conducted an experiment with fruit flies that offer DNA evidence as to why women live longer than men. According to the Global Life Expectancy of 2012, women live on average about six to seven years longer than men in most first-world countries. Previous experiments have also shown a link between the mutation rate of mitochondrial DNA (mtDNA) and aging in humans (and others animals, such as fruit flies). Because only women pass on mtDNA and not men, geneticists decided to conduct an experiment to test the effects of mtDNA on both male and female species. To do this, they standardized the nuclear genomes of a large group of fruit flies and then inserted mtDNA from thirteen different populations of fruit flies from around the world. With the only significant variable being the type of mtDNA, they recorded how long each fruit fly lived. They found that male fruit fly life varied much more significantly than female fruit fly life; therefore, this was strong evidence that mtDNA has much to do with the rate of aging in males and very little to do with aging in females.
So why does mtDNA not affect the aging of females? Because females pass on the mtDNA, they are more prone to adapt overtime through natural selection as oppose to males. If a male has a beneficial mutation that gives him an advantage over others in his species, he will not be able to pass this down to succeeding generations. If a female, however, has a beneficial mutation, then she will be able to pass this down. Thus, overtime, females are able to become more “fit” through natural selection overtime while males are not.