The Y chromosome is not vanishing(nature.com) |
The Y chromosome is not vanishing(nature.com) |
That's interesting! Let's ask the google:
Although they have no Y chromosome, this species still has males and females. In the opinion of Asato Kuroiwa, an associate professor at Hokkaido University, "A new gene formed within an autosome, replaced SRY and became the switch that determines gender." [0]
[0] http://ajw.asahi.com/article/behind_news/social_affairs/AJ20...
ISTM that there must have been some period during which both the new gene and SRY were present in the breeding population, and the inheritance of either (or both) would have produced a male. Since we're talking about fairly small populations on these islands, it was just luck that caused SRY to disappear before the new gene. I doubt we'll see this occur in larger, more-geographically-distributed populations.
The Y chromosome contains vital genes, for males, that code for things males need. Its really pretty much that. Take away the Y chromosome and most mammal species aren't going to survive. Even the rats that lost it had the equivalent genes on the X chromosome. The gene expression of females isn't the same as males in short. In spite of the fact that females and males share an X chromosome.
In women, one of the X chromosomes is inactivated, so it’s almost like that each cell has only one (active) X chromosome. The shared part is not inactivated. So both men and women have two active copies of these parts, and only one active copy of the not shared parts.
Read: http://en.wikipedia.org/wiki/X-inactivation
More specifically: http://en.wikipedia.org/wiki/X-inactivation#Expressed_genes_...
That said, I don't think it's possible to create a fully fertile male by forgoing the chromosome and just giving hormones - there might be some very few sex-specific proteins on it, but I think it depends on the species.
"""
The Y has been stable for the past 25 million years, scientists say. And a major reason is that many of its remaining genes are crucial to the survival of all humans, going far beyond sex determination. There are genes that affect protein synthesis, how active a gene is, and others that splice RNA segments together. They are found in the heart, the blood, the lungs, and other tissues throughout the body. “These are powerful players in the central command room of cells,” says David Page
"""
Some genome sizes, the marbled lungfish carries a lot of weight in its cellular nuclei.
ftp://www.fourmilab.ch/pub/goldberg/sizes.html
From what I can tell the text doesn't contain a lot of new or surprising information, but it does present it in a misleading way.
It's clear that sexual dimorphism in humans is profound in some respects and superficial in others. Since the Y chromosome regulates sexual development, and since males do get some metabolic modifications, saying the Y influences protein synthesis in vital tissues is mostly a truism.
Saying that for example autoimmune diseases with lopsided sex distributions are not connected to sex determination is a fruitless semantics game disconnected from the actual science. To be fair, it's not any more sensationalist than the "rotting Y chromosome" spiel which has been in the press earlier, but all of this is really more a testament to all the things that are wrong with science reporting (and the scientists who enable it) than anything else.
The article does makes a point that unimportant genes have been eliminated from the Y. However, if the remaining genes and relevant proteins are beneficial (as opposed to mandatory), then it would still make sense in the [very] long run that those genes would migrate to some other chromosome, be beneficial also for female homo sapiens, and then get eliminated out of the Y as redundant there (since they'd be somewhere else for both genders already)
FWIW, biology was the one science course I never took, so I have no idea what I'm talking about.
Haha, maybe so, I guess that's a matter of definitions...
I was reading the statement as SRY moves to an autosome and then some other process regulates expression.
SRY translocation is not unheard-of (cf. SRY-positive 46,XX testicular "disorder"), but that's not what Prof. Kuroiwa is saying. He's talking about a change that allows a different gene to code the same proteins that SRY codes. That change could be to the gene in question, or to something else that governs how it is expressed. There's a whole family of genes (SOX) that exist all over, on both allosomes and autosomes, which are similar to SRY, and one would imagine these might substitute for it. Looking around a bit more, I find wikipedia links to a paper [0] that claims the substitute SRY is actually a group of multiple genes on X, which group of genes did translocate from Y. Fascinating stuff!
Sure, if we could then biological sex wouldn't matter quite so much, but until we are, the old Y chromosome is still rather important.
That said, part of me would prefer is we didn't need to rely on non-built-in means to propagate. The idea of becoming utterly reliable on a particular piece of technology for our survival as a species isn't one I'm fond of.