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Jan. 19th, 2018
Sorry, Guys: Your Y Chromosome May Be Doomed But don’t worry, men aren’t going anywhere.
Winnowed (excerpted), copied and edited in various places so go read the original
The Y chromosome 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. It has degenerated rapidly, leaving females with two perfectly normal X chromosomes, but males with an X and a shrivelled Y. If the same rate of degeneration continues, the Y chromosome has just 4.6m years left before it disappears completely.
166m years ago, in the very first mammals, the early “proto-Y” chromosome was originally the same size as the X chromosome and contained all the same genes. However, Y chromosomes have a fundamental flaw. 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.
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. Deprived of the benefits of recombination, Y chromosomal genes degenerate over time and will eventually be lost from the genome.
The Y chromosome has developed some pretty convincing mechanisms to “put the brakes on”, slowing the rate of gene loss to a possible standstill.
In a recent Danish study, published in PLoS Genetics, sequenced portions of the Y chromosome from 62 different men 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.
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. 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.
Even if the Y chromosome in humans does disappear; Japanese spiny rats and mole voles* have lost their Y chromosomes entirely; it does not necessarily mean that males themselves are on their way out. Even in those species that have actually lost their Y chromosomes completely, males and females are both still necessary for reproduction.
In these cases, the SRY “master switch” gene that determines genetic maleness has moved to a different chromosome, meaning that these species produce males without needing a Y chromosome. However, the new sex-determining chromosome—the one that SRY moves on to—should then start the process of degeneration all over again due to the same lack of recombination that doomed their previous Y chromosome.
However, the interesting thing about humans is that while the Y chromosome is needed for normal human reproduction, many of the genes it carries are not necessary if you use assisted reproduction techniques. This means that genetic engineering may soon be able to replace the gene function of the Y chromosome, allowing same-sex female couples or infertile men to conceive. However, even if it became possible for everybody to conceive in this way, it seems highly unlikely that fertile humans would just stop reproducing naturally.
Read more: https://www.smithsonianmag.com/science-nature/y-chromosome-may-be-doomed-180967887/#lDBYDySBZF1u7WDY.99
This article was originally published on The Conversation.
image: https://counter.theconversation.com/content/90125/count.gif
The Conversation
Darren Griffin, Professor of Genetics, University of Kent
Peter Ellis, Lecturer in Molecular Biology and Reproduction, University of Kent
*
The Transcaucasian mole vole (Ellobius lutescens) is a species of rodent in the family Cricetidae. It is found in Armenia, Azerbaijan, Georgia, Iran, and Turkey.
Chromosomes: The karyotype has a low, odd, diploid number, 2n = 17,X. Transcaucasian mole voles have no SRY gene or Y chromosome; both sexes have an XO sex chromosome set, a state possibly derived from an ancestral population in which males had an XX sex chromosome set, like E. tancrei. Their sex-determination method remains unknown.
https://en.wikipedia.org/wiki/Transcaucasian_mole_vole
Winnowed (excerpted), copied and edited in various places so go read the original
The Y chromosome 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. It has degenerated rapidly, leaving females with two perfectly normal X chromosomes, but males with an X and a shrivelled Y. If the same rate of degeneration continues, the Y chromosome has just 4.6m years left before it disappears completely.
166m years ago, in the very first mammals, the early “proto-Y” chromosome was originally the same size as the X chromosome and contained all the same genes. However, Y chromosomes have a fundamental flaw. 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.
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. Deprived of the benefits of recombination, Y chromosomal genes degenerate over time and will eventually be lost from the genome.
The Y chromosome has developed some pretty convincing mechanisms to “put the brakes on”, slowing the rate of gene loss to a possible standstill.
In a recent Danish study, published in PLoS Genetics, sequenced portions of the Y chromosome from 62 different men 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.
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. 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.
Even if the Y chromosome in humans does disappear; Japanese spiny rats and mole voles* have lost their Y chromosomes entirely; it does not necessarily mean that males themselves are on their way out. Even in those species that have actually lost their Y chromosomes completely, males and females are both still necessary for reproduction.
In these cases, the SRY “master switch” gene that determines genetic maleness has moved to a different chromosome, meaning that these species produce males without needing a Y chromosome. However, the new sex-determining chromosome—the one that SRY moves on to—should then start the process of degeneration all over again due to the same lack of recombination that doomed their previous Y chromosome.
However, the interesting thing about humans is that while the Y chromosome is needed for normal human reproduction, many of the genes it carries are not necessary if you use assisted reproduction techniques. This means that genetic engineering may soon be able to replace the gene function of the Y chromosome, allowing same-sex female couples or infertile men to conceive. However, even if it became possible for everybody to conceive in this way, it seems highly unlikely that fertile humans would just stop reproducing naturally.
Read more: https://www.smithsonianmag.com/science-nature/y-chromosome-may-be-doomed-180967887/#lDBYDySBZF1u7WDY.99
This article was originally published on The Conversation.
image: https://counter.theconversation.com/content/90125/count.gif
The Conversation
Darren Griffin, Professor of Genetics, University of Kent
Peter Ellis, Lecturer in Molecular Biology and Reproduction, University of Kent
*
The Transcaucasian mole vole (Ellobius lutescens) is a species of rodent in the family Cricetidae. It is found in Armenia, Azerbaijan, Georgia, Iran, and Turkey.
Chromosomes: The karyotype has a low, odd, diploid number, 2n = 17,X. Transcaucasian mole voles have no SRY gene or Y chromosome; both sexes have an XO sex chromosome set, a state possibly derived from an ancestral population in which males had an XX sex chromosome set, like E. tancrei. Their sex-determination method remains unknown.
https://en.wikipedia.org/wiki/Transcaucasian_mole_vole
Trying Not to Get Sick?
Jan. 19th, 2018 10:31 pmTrying Not to Get Sick? Science Says You’re Probably Doing It Wrong
Cold and flu viruses transfer in very different ways than we think
It’s that time of year again: coughing, wheezy, sticky people all around you, and that dread in the pit of your stomach that you’re about to get sick. What do you do? Conventional wisdom says that to avoid spreading colds or the flu, you should wash your hands frequently—ideally using antibacterial soap—and cover your mouth when you cough.
But it turns out that sometimes, conventional wisdom is just wrong (sorry about that, mom!). We pored through scientific studies and talked to medical experts to find that some of these oft-repeated tips don’t tell the whole story—while others might actually be harmful. Here’s the truth about colds and the flu. (Spoiler: You should still cover your mouth when you cough.*)
*A face mask is good to protect others from your germs if you're sick.
So how do you really avoid getting sick this season? "Avoid people who are sick," he says. "Especially kids … I call them germbags. Don't be a schoolteacher, don't be a pediatrician, don't be a grandparent." Easy enough, right? Oh, and get a flu shot. In a good season, it's about 70 percent effective at preventing flu; even if you're not the type to get sick, it may prevent you from carrying viruses and passing them on to another person, Swartzberg says.
Read more: https://www.smithsonianmag.com/science-nature/theres-more-to-fighting-flu-covering-your-mouth-180961404/#gAkDDHJqJsy7BFyi.99
Am not a teacher.... but just about the same as far as exposure and also am a grandparent who just happens to have a grandchild sick with the flu. Haven't visited for several weeks so that last exposure risk doesn't apply. btw If you didn't hear it yet, the current year's flu shot is mainly ineffective against what is causing the latest flu outbreak.
Cold and flu viruses transfer in very different ways than we think
It’s that time of year again: coughing, wheezy, sticky people all around you, and that dread in the pit of your stomach that you’re about to get sick. What do you do? Conventional wisdom says that to avoid spreading colds or the flu, you should wash your hands frequently—ideally using antibacterial soap—and cover your mouth when you cough.
But it turns out that sometimes, conventional wisdom is just wrong (sorry about that, mom!). We pored through scientific studies and talked to medical experts to find that some of these oft-repeated tips don’t tell the whole story—while others might actually be harmful. Here’s the truth about colds and the flu. (Spoiler: You should still cover your mouth when you cough.*)
*A face mask is good to protect others from your germs if you're sick.
So how do you really avoid getting sick this season? "Avoid people who are sick," he says. "Especially kids … I call them germbags. Don't be a schoolteacher, don't be a pediatrician, don't be a grandparent." Easy enough, right? Oh, and get a flu shot. In a good season, it's about 70 percent effective at preventing flu; even if you're not the type to get sick, it may prevent you from carrying viruses and passing them on to another person, Swartzberg says.
Read more: https://www.smithsonianmag.com/science-nature/theres-more-to-fighting-flu-covering-your-mouth-180961404/#gAkDDHJqJsy7BFyi.99
Am not a teacher.... but just about the same as far as exposure and also am a grandparent who just happens to have a grandchild sick with the flu. Haven't visited for several weeks so that last exposure risk doesn't apply. btw If you didn't hear it yet, the current year's flu shot is mainly ineffective against what is causing the latest flu outbreak.