Do women have more DNA than men?

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  • #1
jerromyjon
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I could be wrong I haven't checked, but women have 2 x's and men have an x and a y. So is an x more DNA than a y?
 

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  • #3
jerromyjon
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Yes. The X chromosome has about 3 times the number of base pairs as the Y.
I was starting with the premise that 4 legs is 1/3 more than 3 legs... but 3 times? Wow. Is that geometrically justified?
 
  • #4
Ygggdrasil
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A diploid human cell contains about 6.5 billion base pairs of DNA. Each X-chromosome is about 0.16 billion base pairs, whereas the Y-chromosome is 0.06 billion base pairs. Therefore, female diploid human cells will contain about 1.5% more DNA than a male diploid human cell.

Note that in female human cells, the cells essentially crumple up and ignore one copy of their X-chromosomes, and only use one copy of their two X-chromosomes, so that extra DNA does not have major effects on cells aside from specifying the sex of the individual.
 
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  • #5
jim mcnamara
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@jerromyjon

Search for the Barr bodies. Tell us what you find. So does this mean the male or the female has more DNA in the nucleus of somatic cells?

(you asked so you get to do some searching... and a little thinking, too.) Another term for this is the Lyon hypothesis.
 
  • #6
epenguin
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The Y chromosomes is not only smaller than X, but it has much fewer genes. At first sight most of the time but might not matter, because as was said half of the female X chromosomes are inactivated anyway.The problem for males is when one of the genes on an X is defective. That leads to both mild conditions like colourblindness and devastating ones like Lechs-Nyhan Syndrome and others (called X-linked diseases). The female with the same defective gene is OK because although one X chromosome is inactivated, it is not the same one in all cells i.e. half the cells will produce the normal gene product and that is usually sufficient for normal health and functioning.

Question said men and women but the same mechanism applies in placental mammals generally, but the story is different beyond that limited group.
 
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  • #7
jim mcnamara
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Thanks @epenguin

I knew the answer. - I hoped @jerromyjon would take the time and thought to work with it a little. Guess not. Did you see the penguin post about the Adelie colonies on Danger Island? ...assuming your interest in your fellow Sphenisciformes.
 
  • #8
Drakkith
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I was starting with the premise that 4 legs is 1/3 more than 3 legs... but 3 times? Wow. Is that geometrically justified?

The Y chromosome is not Y-shaped, nor is a single copy of the X chromosome X-shaped. Below you can see an XY pair of a human male. You'll notice that the X chromosome is must larger than the Y chromosome. Note that if we count the X chromosome as being three 'units' in size and the Y as being one unit, an XX pair is 6 units in size while an XY pair is 4 units (~312 Mbp vs ~213 Mbp). So women have roughly 100 million more base-pairs than men.

Human_male_karyotpe_high_resolution_-_XY_chromosome_cropped.jpg
 

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  • #9
okmj4ongokrwe
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The Y chromosome is not Y-shaped, nor is a single copy of the X chromosome X-shaped. Below you can see an XY pair of a human male. You'll notice that the X chromosome is must larger than the Y chromosome. Note that if we count the X chromosome as being three 'units' in size and the Y as being one unit, an XX pair is 6 units in size while an XY pair is 4 units (~312 Mbp vs ~213 Mbp). So women have roughly 100 million more base-pairs than men.

View attachment 221709
False, the second X chromesone is turned off.
 
  • #10
JT Smith
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Note that in female human cells, the cells essentially crumple up and ignore one copy of their X-chromosomes, and only use one copy of their two X-chromosomes, so that extra DNA does not have major effects on cells aside from specifying the sex of the individual.

I thought it was more complicated than that. Isn't there a random distribution of cells in the body with one or the other X chromosome active? And aren't there often active genes even on the "inactive" chromosome?

I foster kittens as a kind of hobby and it's the reason I've read for the color distribution in certain female cats (e.g. Calico).
 
  • #11
Drakkith
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False, the second X chromesone is turned off.
I never mentioned anything about active or inactive base pairs.
 
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  • #12
BillTre
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X-chromosme inactivation in mammals happens after many cells have already formed in the developing embryo. Once an X-chromosome is inactivated, it stays that way in all descendant cells.
Which chromosome is inactivated is random among the cells in the embryo, so the embryo and the adult that grows from it are a mix of cells with one or the other of its X-chromosomes inactivated.
This can lead to mosaic genetic effects for genes on the X-chromosome.
 
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  • #13
Godot_
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IMHO the question is imprecise...

Above are plenty of answers for "Does a female cell have more DNA than a male cell?", where the answer is "Yes... ...generally it does."

---begin-qualified-nitpicking-------------------------------------

- First caveat here: Not included are 45 X0 genotype women, whose cells ofc have less DNA than male ones.
- Neither are 47 XXY, 47 XYY, ... phenotypical males. The formers' cells do ofc have more DNA that yo standard 46 XX cells.

My bigger issue, though, is that men on average have a higher body weight, more muscle cells (which have plenty of nuclei), a larger and more branched respiratory, cardivascular and digestive system, all of which are lined by endo- and/or epithelia, which again consist of plenty of rather small cells that all have their respective nuclei.

---end-qualified-nitpicking----------------------------------------

So, in terms of DNA per individuum, maybe even on the basis of DNA per kg body weight, men should be expected to have more DNA than women (on the average).

But I'm currently too lazy/busy to look it up for doing the math for quatifying and/or qualified sourcing. If need be I can do that as a followup in two weeks or so.

BTW the answer @ quora (which I found when doing a quick google search) is roughly the same...
 
  • #14
jim mcnamara
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Aneuploidy is a genetic disorder where the total number of chromosomes doesn't equal 46. If there's an extra chromosome copy (trisomy), the result 47 chromosomes. Missing a chromosome copy (monosomy), means 45 total chromosomes. Most "missing (<46)" chromosomes result in severe problems.

- Thompson & Thompson Genetics in Medicine

This is what @Godot_ is discussing. Aneuploidy can result in profound and varying medical problems for patients. There is a long list of other kinds of considerations here. Patient populations are small, so physicians may not encounter them. Some things to note:

To be a bit pedantic,
Cri du chat syndrome: results from a missing part (an arm) of a chromosome.
https://pubs.rsna.org/doi/10.1148/92.1.50

Somatic DNA (mitochondrial "plasmid") damage:
Kearns-Sayre syndrome is a somatic DNA delete, generally ranging from 1 kilobyte to larger deletions - commonly results in cardiomyopathies, ophthalmic myopathies, and proprioception problems. It is (thought to be) inherited via the cytosol in the maternal egg. Sometimes called a somatic mutation.
https://rarediseases.info.nih.gov/diseases/6817/kearns-sayre-syndrome.

FWIW: humans mitochondrial DNA represents about 1% of total cellular DNA (about 1000 to 10,000 copies per cell)
Human Mitochondrial DNA: Particularities and Diseases - PMC
https://www.ncbi.nlm.nih.gov › articles › PMC8533111

I'm not going to enumerate further. But what constitutes a good answer to the original uninformed question depends in part on your point of view.

Interesting topic.
 
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  • #15
epenguin
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False, the second X chromesone is turned off.
Seems not to have read anything of the preceding posts.
 
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  • #16
epenguin
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I foster kittens as a kind of hobby and it's the reason I've read for the color distribution in certain female cats (e.g. Calico).
yes, calico/tortoiseshell cats are classic oft-quoted examples of genetic mosaicism. Lots of explanations online. Whether you get large patches as with tortoiseshell or something more finely distributed will, it is not hard to surmise, depend what stage, what number of cells of the particular somatic line that gives rise to the definitive tissue, the inactivation process kicks in.

Just a couple among many references for various scientific levels, easily found.


https://medicine.jrank.org/pages/2560/Mosaicism-Mosaic-Expression.html

https://imperialbiosciencereview.com/2021/03/05/why-are-there-tortoiseshell-cats/
 
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  • #17
JT Smith
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So human women are all "calicos" too, just not in terms of something readily visible like hair or skin color. I had assumed the same was true with all female mammals but read yesterday night that with marsupials the paternal X chromosome is the one that is always inactivated. No "calico" kangaroos.
 
  • #18
jim mcnamara
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Look up "Barr body", "Lyon hypothesis", we are getting off track. Female primates are not "calicos". Please stop making up things with only partial information.

Barr Bodies are condensed, inactivated X chromosomes that are typically found exclusively in female mammals.
Period. Cats are not special in this regard.

Also check out the concept of chimeras as seen in cats.
https://www.catological.com/facts-chimera-cats/
Chimeras:
https://en.wikipedia.org/wiki/Chimera_(genetics)
 
  • #19
JT Smith
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Calicos in quotes, i.e. mosaics. Female primates have this quality as @BillTre described. Don't turn this into something personal.
 
  • #20
pinball1970
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X chromosome inactivation means that
I never mentioned anything about active or inactive base pairs.
So in terms of genetic material women DO have more BUT in terms of every X chromosome, 50% are inactive.

I have read about X chromosome inactivation but this was years after UG. From Nick Lane possibly? I have no recollection from uni about Lyon which was in the 1960s so I assume it would have been part of the course which was in the 80s.
Anyway I have read the thread with posts from yourself @BillTre and @jim mcnamara this has allowed me to join some dots regarding a particular thing. I will start a new thread on it because it strays a from the OP
 

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