![symbol for female genetics symbol for female genetics](https://cdn1.vectorstock.com/i/1000x1000/25/20/dna-icon-genetics-human-chromosome-symbol-on-gold-vector-20402520.jpg)
This in turn can ultimately drive the formation of entirely new species. In a 2016 paper, she points out that Japanese spiny rats and mole voles have lost their Y chromosomes entirely-and argues that the processes of genes being lost or created on the Y chromosome inevitably lead to fertility problems. The debate therefore continues.Ī leading proponent of the leave argument, Jenny Graves from La Trobe University in Australia, claims that, if you take a long-term perspective, the Y chromosomes are inevitably doomed-even if they sometimes hold on a bit longer than expected. But the leavers say that all they are doing is allowing the Y chromosome to cling on by its fingernails, before eventually dropping off the cliff. The latter group argues that its defence mechanisms do a great job and have rescued the Y chromosome. On the question of whether the Y chromosome will actually disappear, the scientific community, like the UK at the moment, is currently divided into the “leavers” and the “remainers”. Writing in Molecular Biology and Evolution recently, researchers give evidence that this increase in gene copy number in mice is a result of natural selection. These amplified genes play critical roles in sperm production and (at least in rodents) in regulating offspring sex ratio. Looking to other species (Y chromosomes exist in mammals and some other species), a growing body of evidence indicates that Y-chromosome gene amplification is a general principle across the board. They recorded a high rate of “gene conversion events” within the palindromic sequences on the Y chromosome-this is basically a “copy and paste” process that allows damaged genes to be repaired using an undamaged back-up copy as a template. The study also showed that the Y chromosome has developed unusual structures called “palindromes” (DNA sequences that read the same forwards as backwards-like the word “kayak”), which protect it from further degradation. Deprived of the benefits of recombination, Y chromosomal genes degenerate over time and are eventually lost from the genome.Ĭhromosome Y in red, next to the much larger X chromosomeĭespite this, recent research has shown that the Y chromosome has developed some pretty convincing mechanisms to “put the brakes on”, slowing the rate of gene loss to a possible standstill.įor example, a recent Danish study, published in PLoS Genetics, sequenced portions of the Y chromosome from 62 different men and found that it is prone to large scale structural rearrangements allowing “gene amplification”-the acquisition of multiple copies of genes that promote healthy sperm function and mitigate gene loss. This means that genes on the Y chromosome cannot undergo genetic recombination, the “shuffling” of genes that occurs in each generation which helps to eliminate damaging gene mutations. Unlike all other chromosomes, which we have two copies of in each of our cells, Y chromosomes are only ever present as a single copy, passed from fathers to their sons. However, Y chromosomes have a fundamental flaw. The early “proto-Y” chromosome was originally the same size as the X chromosome and contained all the same genes. If we rewind the clock to 166m years ago, to the very first mammals, the story was completely different. The Y chromosome hasn’t always been like this. This may sound like a long time, but it isn’t when you consider that life has existed on Earth for 3.5 billion years. If the same rate of degeneration continues, the Y chromosome has just 4.6m years left before it disappears completely.
![symbol for female genetics symbol for female genetics](https://image.shutterstock.com/image-vector/dna-genetic-symbol-people-man-600w-340539308.jpg)
What’s more, the Y chromosome has degenerated rapidly, leaving females with two perfectly normal X chromosomes, but males with an X and a shrivelled Y. Women, after all, manage just fine without one. Although it carries the “master switch” gene, SRY, that determines whether an embryo will develop as male (XY) or female (XX), it contains very few other genes and is the only chromosome not necessary for life.
![symbol for female genetics symbol for female genetics](https://www.fireupfitness.com/wp-content/uploads/2016/05/inner-thigh-workout.jpg)
The Y chromosome may be a symbol of masculinity, but it is becoming increasingly clear that it is anything but strong and enduring.