X and Y Chromosomes and Identity

[sunnyfield]

Let me say right off that I am not a Biologist, Geneticist, or even a student.

I watched an episode of "Through the Wormhole" and it brought up some things I want to understand better, but I don't know where to begin finding out. I actually have a couple of questions : 1) It is my understanding that the X chromosomes in the female actually get mixed up from one generation to the next , so that the female , when passing down an X in an egg, passes a chromosome that is not an identical copy of one of the ones she received herself. It is a mixture of different genes from each X. (2) The Y chromosome is passed down intact just as received from the father, and his father before him - so in other words , my Y is the same as my fathers and his fathers before him, all the way back generations .

Is this a correct understanding? I really appreciate any help I can get with this . I want to understand this subject better.

[ewmon]

You're right.

 

The mother has two X chromosomes; recombination (ie, mixing) can/does occur, and she passes down a recombined X chromosome (that's almost guaranteed to be different for every egg) to all her offspring.

 

The father has one X and one Y chromosome; recombination cannot occur between them. He can only pass down his X chromosome to his daughter-to-be just as he received it from his mother, and he can only pass down his Y chromosome to his son-to-be just as he received it from his father.

 

These videos explain this (and more) very well, and all of them are worth watching,

 

There's also the correlation between surnames and Y chromosomes due to both being "inherited" from only the father. (But if mom "jumps the fence", then all bets are off.)

[sunnyfield]

Thank you very much! I will watch those videos. I really appreciate your help.

The reason I am trying to grasp this is because there always seems to be a sort of misrepresentation by scientists on these television programs. I realize that it may be because TV wants to "sex it up" for the public to make the show more shocking and get people's attention, and I also think a lot of the time there is misrepresentation because the geneticist being interviewed is a woman - and sometimes these women may be feminists or maybe have issues with men in their personal life. But as I said, maybe it is just for ratings.

The perspective that seems to be so commonly presented is that women have more genes than men, because of the larger number of genes on the X, and therefore have some genetic superiority. One woman even said that this is an inferiority of the male and that eventually it will lead to extinction of men because the Y cannot repair itself. Furthermore the Y is portrayed as a little stunted version of the X. I have listened to this sort of thing and pondered it, a perspective growing in my mind from the information I have been taking in . My take on it is this: The Y is not a stunted version of the X, but a special "mantle" of Identity passed from father to son , a relationship that does not exist with mother to daughter. The fact that women have two X's just means there is a lot of redundancy. Women are in fact missing a special piece of information - an extra piece of information, if you will.

This is particularly relevant to me because of my Jewish heritage from my biological father. According to Jewish tradition , a person is not a Jew unless his mother was. This makes no sense to me . It certainly is not Biblical. And it also makes no sense in light of the subject of this thread. I am quite Jewish - my Y goes back to Biblical times if the above information is true. That is why I titled the thread as I did : "X and Y Chromosomes and Identity".

So to sum up : Men have a special inheritance from there fathers, a special chromosome that more solidifies their identity, not a lesser genetic make-up, but an extra piece of information.

Please forgive my pro-male stance, I know it is upsetting...lol.

[CharonY]

I doubt that there are any serious scientist (in the biological area that is) that subscribe to either of the notion you described. At least not in the presented form. Functionally, line of inheritance is as such not terribly special either way, as as quantity of genes means little in terms of function. it is all about organization and interplay. Just to give a rough idea, the difference in number of genes between humans and a simple bacterium is somewhere between 5-10 fold only. Thus making any kind of inference based on numbers alone (either way) is a bit silly.

 

I believe what you may have heard is that in males are more susceptible to X-chromsomal diseases, as they are basically homozygous, whereas women can be heterozygous and thus do not express he phenotype.

 

 

As for the other assumption, we all share too many alleles (and all the genes) to make a distinction like "Jewish" meaningful in any genetic sense. The only difference are probably highly inbred populations. These tend to have a very high occurrence of genetic defects, for example.

 

But if one does an in-population study (i.e. just focusing on a particular group), Y linkage indeed should show less variability than X linkage (with all the disadvantages that may entail). From a biological viewpoint any assumption of specialness is just human inference rather than of any real biological basis.

 

One thing that I wanted to add, there is a limited recombination between X and Y, too.

[sunnyfield]

The show was "Through the Wormhole " , the episode was "Will Sex Become Extinct" . If you want to see what I am referring to as far as how they presented the subject.

[Moontanman]

It is true that mitochondrial DNA only comes from the mother and can be used to trace populations...

[sunnyfield]

I watched the videos from one of the sites above, and I was interested in the Autosomal DNA - I really never had that sorted out. I knew they say we have two chromosomes, and I remember being taught that we have 23 pairs of chromosomes - but I had not until now understood the difference between the two types of DNA. So "Autosomes" are not "Chromosomes" ? We have two chromosomes and 22 pair of autosomes? And then there is mitochondrial DNA which is passed down separately - fascinating.

I hope I am not a drag for the rest of you - I know my questions are rudimentary. But I appreciate the help. It is hard to look things up with something like this, if you don't know the proper way to phrase a question or how to ask the right question. With that said, if there is a more appropriate forum for someone like me , please let me know.

Moontanman, are your Youtube posts about genetics?

[Moontanman]

I watched the videos from one of the sites above, and I was interested in the Autosomal DNA - I really never had that sorted out. I knew they say we have two chromosomes, and I remember being taught that we have 23 pairs of chromosomes - but I had not until now understood the difference between the two types of DNA. So "Autosomes" are not "Chromosomes" ? We have two chromosomes and 22 pair of autosomes? And then there is mitochondrial DNA which is passed down separately - fascinating.

I hope I am not a drag for the rest of you - I know my questions are rudimentary. But I appreciate the help. It is hard to look things up with something like this, if you don't know the proper way to phrase a question or how to ask the right question. With that said, if there is a more appropriate forum for someone like me , please let me know.

Moontanman, are your Youtube posts about genetics?

 

 

No they are not, I am just like you, trying to learn.

[sunnyfield]

I am curious what others here think about the way such subjects are handled on television programs. As I said earlier , there seems to be a spin put on things - anyone else notice what I am talking about?

[ewmon]

The perspective that seems to be so commonly presented is that women have more genes than men, because of the larger number of genes on the X, and therefore have some genetic superiority. One woman even said that this is an inferiority of the male and that eventually it will lead to extinction of men because the Y cannot repair itself.

Offhand, I don't know where to find what I wrote below on the Internet.

 

When looking at achievement in general, I have read that, in comparison to females, males have relatively more "failures" (low IQ, learning disabilities, ADHD, autism, etc), but they also have more "successes" (high IQ, inventions, discoveries, etc). The idea is that, if you view each gender's achievement as a bell curve, the males' bell curve is more spread out (that is a larger sigma), and the female's bell curve is tighter. The idea being that Nature plays it safe with females, while allowing males to be more of a wild card.

 

 

If I'm remembering this correctly, this theory posits that this phenomenon supposedly stems from females having two X chromosomes and males having only one. If there's a significant genetic mutation in one of the genes on one of the X chromosomes, the female can usually rely on the other X chromosome to provide a tried-and-true copy of it, but the male does not have this redundancy, and so, the consequences of that genetic mutation will express itself in the male, for better or worse.

 

So, from this perspective, males are not inferior, but instead, they are the "test platform" for the one X chromosome that they carry, and so, males are instrumental in the advancement of the species (or at least our X chromosome). I don't know how true this is, but it makes a lot of sense to me.

 

On the other hand, I can't agree about the extinction of men supposedly because the Y cannot repair itself. Maybe one male's lineage will go extinct due to his faulty Y chromosome, but there's plenty of other males with perfectly healthy Y chromosomes — and perhaps/probably there's a man out there somewhere with an enhanced Y chromosome.

 

And, here's an article on the theory that the male Y chromosome might be evolving the fastest.

Edited July 17, 2013 by ewmon

[sunnyfield]

Thanks Ewmon. Very interesting post. I love a good link .

You bring up an interesting subject - innovation .

[CharonY]

With regards to the extinction part, I remember faintly that issue, and I think it was based on extrapolation with bad math that was subsequently blown up in public space but had little impact on the science side.

The thing is that the Y chromsome has little potential to degrade further as anything more would be negatively selected against.

 

 

See for example "Strict evolutionary conservation followed rapid gene loss on human and rhesus Y chromosomes, Hughes et al. 2012, Nature".

[WWLabRat]

I watched the videos from one of the sites above, and I was interested in the Autosomal DNA - I really never had that sorted out. I knew they say we have two chromosomes, and I remember being taught that we have 23 pairs of chromosomes - but I had not until now understood the difference between the two types of DNA. So "Autosomes" are not "Chromosomes" ? We have two chromosomes and 22 pair of autosomes? And then there is mitochondrial DNA which is passed down separately - fascinating.

I hope I am not a drag for the rest of you - I know my questions are rudimentary. But I appreciate the help. It is hard to look things up with something like this, if you don't know the proper way to phrase a question or how to ask the right question. With that said, if there is a more appropriate forum for someone like me , please let me know.

Moontanman, are your Youtube posts about genetics?

 

Sunnyfield, please don't feel negatively about posting your questions here. I can say with absolute certainty that you aren't the only one here that is looking for an outlet to ask these questions. I, myself, have just started my formal education to help put on paper the things I've learned over the years. When it comes to genetics, my understanding is minimal, at best. Because of this, seeing others post about things I've pondered is always refreshing. The important part is that you take away from the questions you ask their respective answers and use it to look at things a bit more in depth. And hopefully from there ask deeper questions. This is, after all, what science is all about.