

The Y chromosome is not vanishing - pwrfid
http://www.nature.com/news/reprieve-for-men-y-chromosome-is-not-vanishing-1.15103?WT.ec_id=NEWS-20140429

======
jessaustin
_She says that two species of spiny rats in Japan have lost the mammalian Y
chromosome completely, shifting many genes to other chromosomes._

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...](http://ajw.asahi.com/article/behind_news/social_affairs/AJ201208230009)

~~~
Locke1689
Curiously, they don't say how the switch in the rats flip-flops. The article
notes that crocodile sex is determined by the temperature of the egg, which is
also fascinating -- but how would it work in mammals?

~~~
jessaustin
My reading of that statement would be that the presence of the hypothesized
"new gene" would produce a male while its absence would produce a female.
After all, that's how SRY works, which it is hypothesized to replace.
Presumably this new gene would code for a very similar set of proteins to that
coded by SRY.

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.

~~~
Locke1689
But wouldn't that just make whatever chromosome carries this gene the new
allosome? I was reading the statement as SRY moves to an autosome and then
some other process regulates expression.

FWIW, biology was the one science course I never took, so I have no idea what
I'm talking about.

~~~
jessaustin
_But wouldn 't that just make whatever chromosome carries this gene the new
allosome?_

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!

[0]
[http://www.ncbi.nlm.nih.gov/pubmed/12900579](http://www.ncbi.nlm.nih.gov/pubmed/12900579)

------
dmm
If the Y chromosomes contains vital genes, then how do women, who don't have a
y chromosome, survive?

~~~
Udo
The Y chromosome doesn't contain vital genes, in fact by chromosome standards
it doesn't contain many genes at all. The primary role of the Y chromosome is
as an activator and modifier of gene programs that reside all over the genome.
This makes sense because the male anatomy is mostly just a modification on top
of female anatomy (preventing some growth here, promoting some other growth
there... done).

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.

~~~
dmm
That's what I thought but then the article says this:

"""

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

"""

~~~
Udo
I guess it depends a bit on what genetic regions we're talking about but to my
knowledge since the Y contains so few genes it's not surprising that almost
none of them changed for a long time. It's already very stripped-down. I'm far
less sure about non-coding regions though, I'd have to check up on that.

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.

------
NAFV_P
Which is more detrimental to the survival of a certain gene, losing vital data
or gaining useless data.

Some genome sizes, the marbled lungfish carries a lot of weight in its
cellular nuclei.

ftp://www.fourmilab.ch/pub/goldberg/sizes.html

------
vajorie
Awww, it's okay boy, you'll survive even if gender is not fixed the way you
thought it were and even if your gender becomes irrelevant.

~~~
talideon
It's not gender identity, but biological sex that's the issue here, which is
kinda important when it comes to reproduction.

~~~
PeterisP
Well, we are close to capability to ignore biological sex when it comes to
reproduction. We probably don't/won't want to ignore it, but if we had to,
then we most likely could make do with artificial means of reproduction that
don't neccessarily need both sexes.

~~~
talideon
But we're not there, and even if we were, the methods are vastly more
expensive and inaccessible than natural methods.

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.

~~~
PeterisP
If we're talking about a chromosome going away quickly, then "quickly" in that
context means at least thousands of generations. We're not there, but it's not
_that_ far away.

~~~
talideon
Oh, I agree, and research down that line is worth pursuing, but until we're at
that point and Y is still important. The implications would be staggering, and
no doubt mostly for the better. It could open up the ability to have children
to so many couples who currently have few options, be they same sex,
infertile, or whatever. The primary downside I can see in the short term is
the effect it would likely have on adoptions.

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.

