On middling , women survive longer than men , at least in berth where the danger of childbirth have been tamed . There are memes offeringexplanations , and doubtless many factors are involved , but a new discipline suggests part of the answer lies in additional ecstasy chromosomes .
Introductory genetics course of action talk about women having two 10 chromosomes , while men have an ecstasy and a Y. The true statement is far more complex . Some people have redundant chromosomes , such as XXY , while cleaning lady withcomplete androgen insensitivity syndromehave an XY combination but female genitalia . That ’s all before consider the complexity transgender people add to the history . Nevertheless , XX women and XY men represent the most common combinations .
Some advantages of have two decade chromosomes are well known . Many genetic diseases , most famously hemophilia , are due to recessive X chromosome mutation . Boys with the faulty reading of the gene digest a in high spirits chance of dying as children . girlfriend are only affected in uncommon face where both their X chromosome carry the mutated variant .
Dr Dena Dubalof the University of California San Francisco has demonstrate that this cover against recessive factor is not the only benefit X chromosome offer , at least in rodents , where females also live longer . Dubal mastermind some mouse to have XX chromosome but male procreative organ and others to have XY genetics but distaff organs . These were compared inAging Cellwith mice that had the conventional mammalian chromosome and sexual activity organ compounding .
Unusually for research lab mouse , the I Dubal was canvass were allow to survive until they died of natural causa . Dubal found that while female sex organs were associated with long lives , the chromosome were still more important . The XX mice , whether they had ovaries or testes , outlived their XY counterparts on average .
Specifically , the XX mice were less potential to go before they reached 23 calendar month onetime , irrespective of their crotch . Those that live to this revered eld ( by black eye standards ) did best if they combined XX chromosome and ovaries .
" One can imagine nature has driven females to evolve this way of life . When you ’re subsist longer , you may really ensure the well - being of your young , and maybe even their progeny , " Dubal said in astatement . This assumes the females are providing more parental care than the males , something that is certainly not rightful for every mintage .
Whatever the evolutionary account , the mechanics remains unknown . Dubal has floated the theory that the Y chromosome may be toxic , but also notes that spare X chromosome are give tongue to in female cells , maybe provide some unidentified protective effect . Dubal ’s specialization is in neurodegenerative diseases like Alzheimer ’s , and she desire to get word if the protective effects of X chromosome can be double , possibly withprotective proteinsto keep our brains sizable longer .
