Scientists at UC Berkeley may have figured out why humans and other species with Y chromosomes tend to have shorter lifespans than their XX-chromosome counterparts. According to their research, our DNA is toxic.
What? Traditionally delineated into male and female, many species can be split into two majority groups consisting of those with XY chromosomes and those with XX chromosomes.
Scientists have long suspected that either the presence of the Y chromosome or the absence of the X was responsible for an observed difference in lifespans between the two DNA types. As it turns out, certain properties of the Y chromosome may ultimately be responsible.
Per the team’s research paper:
Sex-specific differences in lifespan are prevalent across the tree of life and influenced by heteromorphic sex chromosomes. In species with XY sex chromosomes, females often outlive males. Males and females can differ in their overall repeat content due to the repetitive Y chromosome, and repeats on the Y might lower survival of the heterogametic sex.
Why? The research indicates that repetitions in the Y chromosome are the culprit. As people with Y chromosomes age, this “repeat content” activates and produces toxic side-effects.
This link could help explain why humans and other creatures with Y chromosomes typically have shorter lifespans.
But? Almost all chromosomes have repeat content. In fact, most scientists believe the repetitive parts of living creatures’ DNA are essential components for species-wide and individual viability.
This makes narrowing down the “why” of Y chromosome-related lifespan deprecation a tricky challenge.
In interpreting the team’s results, it’s important to note the bulk of their research was conducted on fruit flies. The annoying but mostly harmless insect was chosen because, like humans, it can be split roughly into XY DNA types. But, when compared to humans, fruit flies have significantly more repetition in their Y chromosomes.
This makes them the ideal candidate to support a theory involving toxic DNA repetition, but it’ll take more study to determine how applicable these observations are to humans.
Quick take: A lot of people have Y chromosomes. If scientists can sort out why they tend to live shorter lives than their double-X counterparts, it could help establish potential interventions or genetic therapies for the toxic side-effects of our DNA.