Genetics: Women may live longer than men due to toxic effects of the Y chromosome

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Is THIS why women tend to live longer than men? Repeated sections of the Y chromosome can cause toxic effects as men age, shortening their lifespan

  • Researchers from the US studied fruit flies of the species Drosophila miranda
  • Males of this species have twice as many repeated DNA sections as the females
  • The team found that the reps are released to become active as the flies age
  • This causes ‘toxic’ effects, including impaired memory and DNA damage

Toxic masculinity will be the end of you – literally, if you’re a fruit fly.

US researchers found that as male fruit flies age, repetitive sections in their Y chromosomes become active, causing toxic effects.

Specifically, previous studies on fruit flies have shown that when repeated sections become active, they impair memory, cause DNA damage, and shorten lifespan.

Although both male and female flies carry these repeat sequences, they are more common on the Y chromosome, representing a ‘genomic risk’.

Together, this may explain why – in species with XY sex chromosomes, such as humans – females tend to have a longer lifespan than their male counterparts.

US researchers found that as male fruit flies age, repetitive sections in their Y chromosomes become active, causing toxic effects.  Pictured: X and Y chromosomes

US researchers found that as male fruit flies age, repetitive sections in their Y chromosomes become active, causing toxic effects. Pictured: X and Y chromosomes

In their study, biologist Alison Nguyen and Doris Bachtrog from the University of California, Berkeley studied a species of fruit fly called Drosophila miranda.

Males of this species have twice as much repetitive DNA as their female counterparts – and a significantly shorter lifespan too.

They found that in the cells of young male flies, DNA is held in a tightly packed form and that the repeated sections are turned off.

However, as the flies age, the duo found that the repeated sections can be activated because the DNA forms a looser shape, resulting in the toxic side effects.

“We show that transposable elements on the Y chromosome are silenced less effectively in male Drosophila,” the researchers wrote in their paper.

“The toxic Y effect seems more pronounced in a species that contains a larger Y chromosome with more repeats and more actively transcribed genes.”

“Our data shows that repeating Y chromosomes pose a genomic risk for men,” they concluded.

Previous studies on fruit flies have shown that when repeated sections are unpacked and become active, they impair memory, cause DNA damage and shorten lifespan.  Pictured: Densely packed DNA - or so-called 'heterochromatin' - seen across different chromosomes

Previous studies on fruit flies have shown that when repeated sections are unpacked and become active, they impair memory, cause DNA damage and shorten lifespan. Pictured: Densely packed DNA – or so-called ‘heterochromatin’ – seen across different chromosomes

According to the duo, the findings also support the idea of ​​a more general link between repeated DNA sections and aging, one that is poorly understood for now.

The DNA damage caused by repeated sectioning likely contributes to the physiological effects of aging, they added, but more research is needed to discover the exact mechanisms underlying the toxic effects of repeated DNA.

The full findings of the study have been published in the journal PLOS Genetics.

THE Y CHROMOSOME DECLARED

The Y chromosome is one of two sex chromosomes found in humans – the other is the X chromosome.

It’s the only chromosome in an organism that’s not essential to life – after all, women survive just fine without it.

In humans, the other 22 chromosome pairs – the autosomes – are identical.

The Y chromosome comprises more than 59 million building blocks of DNA and represents almost 2 percent of the total DNA in cells.

But the human Y chromosome is still one of the smallest in the genome.

It is carried by about half of a man’s sperm and determines whether a child will be male or female.

Despite this, it contains very little other important information.

And researchers think it is quickly disappearing.

The number of genes on the Y has dropped from more than 1,000 to about 50, a loss of more than 95 percent.

If the same rate of degeneration continues, the Y chromosome has only 4.6 million years to go before it completely disappears.

But the Y chromosome has not always been this small.

It was once the size of the X chromosome and contained all the same genes.

The problem, however, is that Y chromosomes are only found as a single copy, which are passed from fathers to their sons, rather than a pair.

This means that genes on the Y chromosome cannot undergo something known as ‘genetic recombination’.

This is a gene switching that occurs in every generation that helps eliminate harmful gene mutations.

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