Scientists generate XX and XY cells from a person with Klinefelter syndrome(scientificamerican.com)
scientificamerican.com
Scientists generate XX and XY cells from a person with Klinefelter syndrome
https://www.scientificamerican.com/article/scientists-created-male-and-female-cells-from-a-single-person/
174 comments
What was accomplished here occurs in nature, in a condition called sex-hormone discordant chimerism, where replication errors in embryos result in persons who have a mix of otherwise identical (in terms of genetics) male and female cells in their body. In very rare cases this can result in intersex morphology (https://www.nature.com/articles/s10038-020-0748-4). Generally in mammals, though, such chimerism doesn't result in dramatic phenotypic variance from normal male/female morphology. This is because mammalian secondary sex characteristics expressed by cells are mostly determined by the hormone bath the cells live in, so if a body has wholly or overwhelmingly one-sex gonads, they will develop as that sex. The situation is quite different in insects in birds, where secondary sex characteristics are largely determined by the sex chromosomes of individual cells. This leads to some dramatic phenotypes, such the bilateral gynandromorph (e.g., https://www.birdnote.org/listen/shows/cardinal-thats-half-ma...).
The other difference with birds is that males are the homogametic sex, with ZZ chromosomes, whereas females are the heterogametic sex, with ZW: https://en.wikipedia.org/wiki/ZW_sex-determination_system
But they are trigametic and not bigametic.
FYI I'm pretty sure you meant to link a different nature article, the one you linked is something about methane emissions from wetlands.
parent seems to have fixed it: by following the link, I got an article titled A Cardinal That's Half Male, Half Female.
Thanks for catching that. Fixed.
pavlov(5)
One takeaway is that the genome is highly integrated, i.e. just because there are two sex-linked chromosomes doesn't mean that they aren't also interacting constantly with the other 22 pairs of chromosomes found in every reproducing human cell (and the proteome, and the microbiome, for that matter). From linked paper:
> "Although some of the sex differences arise from hormonal effects (Gurvich et al., 2018), it is now acknowledged that many differences are due to sex chromosome complement (Arnold, 2012). Studying the effects of sex chromosome complement on gene expression and biological phenotypes is impeded by variation in genetic background. Therefore a large sample size is needed to identify sex-related differences (Ronen and Benvenisty, 2014). To date, there is no human model to study sex differences that can overcome the variation in genetic background."
Another complicating factor must be the random nature of X-chromosome inactivation in XX cells, as only one of the two copies is actively transcribed. Hence even if you clone an XX-type cell, its progeny cells will at some point randomly (and permanently) switch off one of those X chromosomes (to avoid making too many gene products).
> "The two X chromosomes have an equal probability of being silenced. Silencing, once established, is stable: the same X chromosome remains inactivated in all subsequent cell generations. As a result, each female is a mosaic of cells in which either the maternally inherited or the paternally inherited X is silenced."
https://jbiol.biomedcentral.com/articles/10.1186/jbiol95
> "Although some of the sex differences arise from hormonal effects (Gurvich et al., 2018), it is now acknowledged that many differences are due to sex chromosome complement (Arnold, 2012). Studying the effects of sex chromosome complement on gene expression and biological phenotypes is impeded by variation in genetic background. Therefore a large sample size is needed to identify sex-related differences (Ronen and Benvenisty, 2014). To date, there is no human model to study sex differences that can overcome the variation in genetic background."
Another complicating factor must be the random nature of X-chromosome inactivation in XX cells, as only one of the two copies is actively transcribed. Hence even if you clone an XX-type cell, its progeny cells will at some point randomly (and permanently) switch off one of those X chromosomes (to avoid making too many gene products).
> "The two X chromosomes have an equal probability of being silenced. Silencing, once established, is stable: the same X chromosome remains inactivated in all subsequent cell generations. As a result, each female is a mosaic of cells in which either the maternally inherited or the paternally inherited X is silenced."
https://jbiol.biomedcentral.com/articles/10.1186/jbiol95
> > Silencing, once established, is stable: the same X chromosome remains inactivated in all subsequent cell generations. As a result, each female is a mosaic of cells in which either the maternally inherited or the paternally inherited X is silenced.
For those curious about it, a visual example of this is tortoiseshell and calico cats.
The orange or black in a cat is X linked. A simple, not quite correct, representation of this would be that a male cat can be either XoY or XbY while a female cat can be XoXo, XoXb, XbXb. The XoXb cats are both black and orange and are frozen at the time when one of the chromosomes were silenced.
This is known as X-inactivation and the Wikipedia page ( https://en.wikipedia.org/wiki/X-inactivation ) even has a picture of a tortoiseshell cat.
For those curious about it, a visual example of this is tortoiseshell and calico cats.
The orange or black in a cat is X linked. A simple, not quite correct, representation of this would be that a male cat can be either XoY or XbY while a female cat can be XoXo, XoXb, XbXb. The XoXb cats are both black and orange and are frozen at the time when one of the chromosomes were silenced.
This is known as X-inactivation and the Wikipedia page ( https://en.wikipedia.org/wiki/X-inactivation ) even has a picture of a tortoiseshell cat.
The other factor unaddressed here is methylation. To form a complete human person, as far as we know, you must have one set of chromosomes from a female imprinted via an ovum and another from a male imprinted via a sperm. If this doesn't take place, you may have strange genetic symptoms. Male bodies deactivate certain genes and reactivate some others so that, when combined with the way in which female bodies do the same thing, the resultant genome has a full set of proteins sufficient to form of a homestatically stable human.
When this goes wrong, genetic disease can occur such as what happens with Angel man and Prader willi syndrome, which is caused by the exact same mutation but dependent on the sex of the parent it was inherited from.
When this goes wrong, genetic disease can occur such as what happens with Angel man and Prader willi syndrome, which is caused by the exact same mutation but dependent on the sex of the parent it was inherited from.
So with X inactivation it sounds like it hardly matters whether the X Chromosome is a duplicate or different, other than any effects that might be seen by having 100% of your cells be behaving a certain way instead of a mix of the two evening some things out. Like metabolism, endocrine and renal function.
[deleted]
> To create such a model, ... [they] ... obtained ... cells previously collected from a person with ... an extra X chromosome
So, the title is rather misleading. They just had to get cells to shed one of the three chromosomes, they didn't get an XX female to somehow produce a Y, nor an XY male to duplicate their X.
So, the title is rather misleading. They just had to get cells to shed one of the three chromosomes, they didn't get an XX female to somehow produce a Y, nor an XY male to duplicate their X.
Hmm. If anyone can suggest a better title (i.e. more accurate and neutral, preferably using representative language from the article), we can change it again.
From the article they specify "with Klinefelter syndrome" which is the XXY version of trisomy 23. This fits the word limit: "Scientists generate XX and XY cells from a person with Klinefelter syndrome"
Ok, let's go with that. Thanks!
None of us will have heard of Klinefelter syndrome before, but maybe that's a good thing.
None of us will have heard of Klinefelter syndrome before, but maybe that's a good thing.
Interesting. It sounds like they used cells from someone with Klinefelter's syndrome (XXY sex chromosomes) but I'm curious if a similar technique could be used to generate male and female cells from any male (XY sex chromosomes). Does anyone on here have an idea of why they needed to start with cells derived from someone with "mosaic" Klinefelter's?
Not a geneticist, but X is not female and Y is not male. Rather, XX is female and XY is male. To make XX from a single XY person would be to clone the X and I would guess would lead to unviability problems when the chromosomes are put to use
Edit: for those downvoting, can you tell me how I’m wrong, if that is the case?
Edit: for those downvoting, can you tell me how I’m wrong, if that is the case?
My understanding is that the master switch for sex determination has been identified as the "SRY" gene normally found on the Y chromosome. Active SRY means development heads down the "male" path in the genes; no SRY (or non-functional SRY) means development heads down the "female" path.
SRY can cross over to the X chromosome (resulting in an XX male), but the end result is usually sterile as there are other genes elsewhere on the Y chromosome that are also necessary for complete development.
SRY can cross over to the X chromosome (resulting in an XX male), but the end result is usually sterile as there are other genes elsewhere on the Y chromosome that are also necessary for complete development.
> for those downvoting, can you tell me how I’m wrong, if that is the case?
Sure. Your claim that X is not female is correct. Your claim that Y is not male is wrong. Y is male. If one or more Y chromosomes are present, a male will develop, and if zero or fewer are present, a female will develop.[1]
Cloning a normal male's single X chromosome would lead to the type of problems familiar from inbreeding, but would be unlikely to lead to nonviability; two different X chromosomes, which all normal women have, are already too many and parts of them must be inactivated so that normal development can proceed.
The Y chromosome is unimportant enough that chromosomal abnormalities generally leave the organism in a viable, if often defective, state. The subject of this experiment is an example, with three (XXY) sex chromosomes. One X chromosome and no Y chromosomes (which would usually be described "XO", not "X") would get you a female with Turner syndrome.
In a handy table:
X alone: female, Turner syndrome
Y alone: male, but nonviable; this will be a miscarriage.
XX: female, normal
XY: male, normal
YY: male, nonviable
XXX: female, triple X syndrome
XXY: male, Klinefelter syndrome
XYY: male, Jacobs syndrome
YYY: male, nonviable
[1] There is an exception related to androgen insensitivity. There you have a genetic male that develops into what is mostly a phenotypic female. Such people have female psychology and female external anatomy, but they do not have a female reproductive system and are therefore sterile.
Sure. Your claim that X is not female is correct. Your claim that Y is not male is wrong. Y is male. If one or more Y chromosomes are present, a male will develop, and if zero or fewer are present, a female will develop.[1]
Cloning a normal male's single X chromosome would lead to the type of problems familiar from inbreeding, but would be unlikely to lead to nonviability; two different X chromosomes, which all normal women have, are already too many and parts of them must be inactivated so that normal development can proceed.
The Y chromosome is unimportant enough that chromosomal abnormalities generally leave the organism in a viable, if often defective, state. The subject of this experiment is an example, with three (XXY) sex chromosomes. One X chromosome and no Y chromosomes (which would usually be described "XO", not "X") would get you a female with Turner syndrome.
In a handy table:
X alone: female, Turner syndrome
Y alone: male, but nonviable; this will be a miscarriage.
XX: female, normal
XY: male, normal
YY: male, nonviable
XXX: female, triple X syndrome
XXY: male, Klinefelter syndrome
XYY: male, Jacobs syndrome
YYY: male, nonviable
[1] There is an exception related to androgen insensitivity. There you have a genetic male that develops into what is mostly a phenotypic female. Such people have female psychology and female external anatomy, but they do not have a female reproductive system and are therefore sterile.
Thanks nicely laid out.
Also not a geneticist, but I'm pretty sure this is wrong because you only get recombination between analogous autosome pairs. The allosomes, or sex chromosomes, you just get from one parent anyway. Females get the X from the mother and the X from the father, but rather than recombination producing an X that is different from either parent, one of them just gets deactivated randomly in every cell during embryonic development and the offspring ends up with a single active X in each cell, usually roughly 50/50 split between exactly the same as the father and exactly the same as the mother. This is true in placental mammals, but in marsupials, it is always the father's X that gets deactivated.
So it seems like making XX from a single XY person would just end up doing something genetically similar to what already happens with marsupials, which doesn't result in non-viability.
Of course, cloning at all does result in not getting genetic diversity you would normally get from recombination, which can eventually result in population-level problems if you're doing enough of it.
So it seems like making XX from a single XY person would just end up doing something genetically similar to what already happens with marsupials, which doesn't result in non-viability.
Of course, cloning at all does result in not getting genetic diversity you would normally get from recombination, which can eventually result in population-level problems if you're doing enough of it.
The recombination happens when the gametes are produced, during meiosis.
While in males there is no recombination between the X and Y chromosomes, in females sometimes there is recombination between the two X chromosomes.
Therefore the X chromosome received by a child from the mother may either be 1 of the 2 X chromosomes of the mother, chosen randomly, or it may be a combination of those 2 X chromosomes.
The inactivation of an X chromosome happens only in the female somatic cells, where the remaining active X chromosome is either the X chromosome of the father or 1 of the 2 X chromosomes of the mother or a combination of the 2 X chromosomes of the mother.
While in males there is no recombination between the X and Y chromosomes, in females sometimes there is recombination between the two X chromosomes.
Therefore the X chromosome received by a child from the mother may either be 1 of the 2 X chromosomes of the mother, chosen randomly, or it may be a combination of those 2 X chromosomes.
The inactivation of an X chromosome happens only in the female somatic cells, where the remaining active X chromosome is either the X chromosome of the father or 1 of the 2 X chromosomes of the mother or a combination of the 2 X chromosomes of the mother.
I suspect that making an XX from the same X would result in expression of all the recessive genes, which would be the ultimate in inbreeding. Probably with quickly fatal consequences.
Consider that in all males, all of the X chromosome genes are expressed.
What's more, with X inactivation, one of the chromosomes in XX becomes almost completely inactive and all of the genes on the other chromosome are expressed.
https://en.wikipedia.org/wiki/X-inactivation
> X-inactivation (also called Lyonization, after English geneticist Mary Lyon) is a process by which one of the copies of the X chromosome is inactivated in therian female mammals. The inactive X chromosome is silenced by being packaged into a transcriptionally inactive structure called heterochromatin. As nearly all female mammals have two X chromosomes, X-inactivation prevents them from having twice as many X chromosome gene products as males, who only possess a single copy of the X chromosome (see dosage compensation).
What's more, with X inactivation, one of the chromosomes in XX becomes almost completely inactive and all of the genes on the other chromosome are expressed.
https://en.wikipedia.org/wiki/X-inactivation
> X-inactivation (also called Lyonization, after English geneticist Mary Lyon) is a process by which one of the copies of the X chromosome is inactivated in therian female mammals. The inactive X chromosome is silenced by being packaged into a transcriptionally inactive structure called heterochromatin. As nearly all female mammals have two X chromosomes, X-inactivation prevents them from having twice as many X chromosome gene products as males, who only possess a single copy of the X chromosome (see dosage compensation).
> What's more, with X inactivation, one of the chromosomes in XX becomes almost completely inactive
There is a huge distance between "almost completely inactive" and "inactive". A Turner's syndrome patient (only one X chromosome) usually has several obvious physical defects, including sterility.
Interestingly, as far as I'm aware the things we usually think of as "X-linked" (more common in men, inherited as a recessive phenotype on the X chromosome - things like red/green colorblindness and male-pattern baldness) aren't as common in Turner's patients as you might expect.
There is a huge distance between "almost completely inactive" and "inactive". A Turner's syndrome patient (only one X chromosome) usually has several obvious physical defects, including sterility.
Interestingly, as far as I'm aware the things we usually think of as "X-linked" (more common in men, inherited as a recessive phenotype on the X chromosome - things like red/green colorblindness and male-pattern baldness) aren't as common in Turner's patients as you might expect.
[deleted]
I think it's because the person you're responding to didn't seem to be implying that a single X or a single y would count?
Instead, they're probably talking about taking three cells with XY, and then using that to create an xx, an xy, and then some leftover parts.
If that is the case, your correction might seem arrogant or assuming.
Instead, they're probably talking about taking three cells with XY, and then using that to create an xx, an xy, and then some leftover parts.
If that is the case, your correction might seem arrogant or assuming.
Seems obvious to me why they led with that clarification and then directly responded to the point of why you might be able to make XX from XXY but not XY.
[deleted]
You're correcting a claim which wasn't made by the GP (Not sure if it has been edited though), as well as calling out that you're being downvoted which is against HN guidelines.
>Please don't comment about the voting on comments. It never does any good, and it makes boring reading.
>Please don't comment about the voting on comments. It never does any good, and it makes boring reading.
I’m pretty sure you’re the one commenting about voting. Their edit asks why they’re wrong and using the fact they are being downvoted to encourage people to reply.
The replies since then have been interesting and not boring at all. Until I got to yours.
The replies since then have been interesting and not boring at all. Until I got to yours.
Fair enough
This individual had T-cells that were: XX, XXY, and XY (mosaic Klinefelters), but otherwise genetically identical. They collected the XX and XY cells and coaxed them into being stem cells. Now researchers can use this stem cell line for research.
I see. So it was more about capturing the cells with the desired chromosomes and converting them to stem cells than about creating cells with the desired chromosomes. Thank you for your explanation!
Doubtful. Males methylate their X chromosomes differently from females during the production of gametes.
Is this basically the approach speculated by Neal Stephenson in Seveneves?
Not really, they didn't all have Klinefelter's syndrome.
[deleted]
The title used to say Male and Female (not XX/XY), and that's the title of the actual article. Normal HN policy is to keep the article title unless it's long or clickbait. Why was it edited?
I can't speak for whoever changed the title, but XX/XY is far more accurate and less clickbaity than Male/Female in this context.
There is far more to human biological sex than the chromosomal distinction. Take an XY cell, but it in an otherwise female body, and it will, in many ways, express itself similar to that of an XX cell. This is the theory behind hormome replacement therapy (HRT).
That is not to say that an XY cell in a female body would be identical to an XX cell in the same. For instance, an XY eye in a female body would likely be similar to a male eye with regards to color blindness; because we have traced colorblindness directly to a chromosonal difference.
However, most sex differences (in humans) are not chromosonal. Instead they are triggered by a single gene (SRY), that just so happens to occur on the Y chromosone. That single gene codes for a protein that triggers almost all of the sex differentiation. Splice that single gene onto a X chromosome and you can get an XX human that appears male.
Exactly what differences are directly chromosomal, and what are developmental is a largly open area of research, and exactly what this achievement hopes to further enable.
There is far more to human biological sex than the chromosomal distinction. Take an XY cell, but it in an otherwise female body, and it will, in many ways, express itself similar to that of an XX cell. This is the theory behind hormome replacement therapy (HRT).
That is not to say that an XY cell in a female body would be identical to an XX cell in the same. For instance, an XY eye in a female body would likely be similar to a male eye with regards to color blindness; because we have traced colorblindness directly to a chromosonal difference.
However, most sex differences (in humans) are not chromosonal. Instead they are triggered by a single gene (SRY), that just so happens to occur on the Y chromosone. That single gene codes for a protein that triggers almost all of the sex differentiation. Splice that single gene onto a X chromosome and you can get an XX human that appears male.
Exactly what differences are directly chromosomal, and what are developmental is a largly open area of research, and exactly what this achievement hopes to further enable.
SRY triggers development of testis, but in fact, if you have a translocation of just SRY onto X, and thus are an XX male, you may have issues with reproduction, as the Y chromosome contains other supporting genes for the production of sperm.
We can go on about male v female as a social construct, but biologically, males produce the smaller gamete, so if one has SRY and has an otherwise male phenotype, but isn't producing sperm, from a strictly biological perspective, it's not at all clear that the statement 'SRY is the determinant of maleness' is necessarily true.
It certainly will make you develop testicles and male secondary sex characteristics.
You are correct on the cell naming. Cells cannot be male or female. That is a characteristic of a complete person. They can be derived from a male or female, but what the scientists did here did not change that attribute of a cell.
We can go on about male v female as a social construct, but biologically, males produce the smaller gamete, so if one has SRY and has an otherwise male phenotype, but isn't producing sperm, from a strictly biological perspective, it's not at all clear that the statement 'SRY is the determinant of maleness' is necessarily true.
It certainly will make you develop testicles and male secondary sex characteristics.
You are correct on the cell naming. Cells cannot be male or female. That is a characteristic of a complete person. They can be derived from a male or female, but what the scientists did here did not change that attribute of a cell.
Just curious, what are the potential effects of CRISPR/Cas9-mediated knock-out of SRY in adult humans?
The article title is a factually incorrect representation of the study being discussed. If you read the article and the study, you'll see the study was about changing chromosomes in a cell line, not about changing the sex of a person.
Everything about primary and secondary sex characteristics would not be affected by changing someone's chromosomes. Homologous sex structures diverge before birth based primarily on dht metabolism. Even then, chromosome expression doesn't always determine how dht will metabolize, meaning whatever chromosomes a person has can still lead to someone having any kind of primary and secondary sex characteristics. The six most common sex chromosome patterns in humans are XX, XY, XXY, XYY, X, and XXXY (in that order).
Sex and gender are both far more complex than merely chromosome expression, and chromosome expression is anything but a binary. This study has nothing to do with being male or female.
Everything about primary and secondary sex characteristics would not be affected by changing someone's chromosomes. Homologous sex structures diverge before birth based primarily on dht metabolism. Even then, chromosome expression doesn't always determine how dht will metabolize, meaning whatever chromosomes a person has can still lead to someone having any kind of primary and secondary sex characteristics. The six most common sex chromosome patterns in humans are XX, XY, XXY, XYY, X, and XXXY (in that order).
Sex and gender are both far more complex than merely chromosome expression, and chromosome expression is anything but a binary. This study has nothing to do with being male or female.
From the article:
> “This is a very well-designed study that validates the notion that sex differences start early in development—and that they depend on the sex chromosomes because that’s the only thing that can account for those differences,” says Nora Engel, a professor of cancer and cell biology at Temple University, who was not involved in this work.
Is this your area of expertise?
> “This is a very well-designed study that validates the notion that sex differences start early in development—and that they depend on the sex chromosomes because that’s the only thing that can account for those differences,” says Nora Engel, a professor of cancer and cell biology at Temple University, who was not involved in this work.
Is this your area of expertise?
It is. And that quote is correct.
There's two problems here. One is that XX/XY is not even a majority of the common human chromosome karyotypes, and changing karyotypes does not change someone's sex characteristics; those are determined at one specific moment during gestation, which may or may not be affected by changing the chromosomes beforehand, but certainly would not be affected by changing their chromosomes after that moment. Primary and secondary sex characteristics are determined by androgen metabolism, not by chromosome karyotypes.
Secondly most of the human karyotypes are not assigned a sex until some time after birth, and XY is often assigned female at birth because the divergence of homologous structures depends on androgen metabolism, not chromosome karyotype. Sex and gender don't exist for cell lines in the same way they do for people.
TL/DR; This is an article about a study that found they could change a cell line's karyotype, not a person's sex characteristics which are determined not by chromosome karyotypes but by androgen metabolism during gestation. Whoever wrote the headline didn't understand the topic.
There's two problems here. One is that XX/XY is not even a majority of the common human chromosome karyotypes, and changing karyotypes does not change someone's sex characteristics; those are determined at one specific moment during gestation, which may or may not be affected by changing the chromosomes beforehand, but certainly would not be affected by changing their chromosomes after that moment. Primary and secondary sex characteristics are determined by androgen metabolism, not by chromosome karyotypes.
Secondly most of the human karyotypes are not assigned a sex until some time after birth, and XY is often assigned female at birth because the divergence of homologous structures depends on androgen metabolism, not chromosome karyotype. Sex and gender don't exist for cell lines in the same way they do for people.
TL/DR; This is an article about a study that found they could change a cell line's karyotype, not a person's sex characteristics which are determined not by chromosome karyotypes but by androgen metabolism during gestation. Whoever wrote the headline didn't understand the topic.
Because it was clickbait and arguably misleading as well.
Note that we replaced it with what the article itself says it's about, once it gets to the stage of actually saying that.
Note that we replaced it with what the article itself says it's about, once it gets to the stage of actually saying that.
[deleted]
I am eagerly anticipating the birth of Henry Lacks.
Haha, pretty good one! Incredible that her cells are still used all over the world long after her death.
The 70-90 chromosomes of the HeLa line may not agree to this easily
Dumb question but how is this different from a women giving birth to either male or female babies ?
I don't know if this totally answers your question but sex is actually determined by the male haploid cells (sperm). Females have XX chromosomes and thus can only produce daughter haploid cells with X chromosomes. Males have XY chromosomes and produce daughter haploids cells with either X or Y chromosomes. The sex of the fertilized zygote is determined by whether an X or a Y chromosome containing sperm reaches the egg.
Besides what other response have said, the X chromosome passed from a mother to an offspring is not typically identical to either of the X chromosomes in her own body. Rather, the X chromosome passed on through her eggs is a blend of her two X chromosomes. This process is called genetic recombination and is basically what allows sexual reproduction to roll new genes.
Since men (typically) only have one X chromosome to start, the X passed in their sperm is identical to that of their somatic cells. So two sisters with the same parents will share one identical X from their father, but the second X from their mother will be different combinations of her two X's.
Edit to add: if genetic recombination didn't happen, then lots of siblings would end up as genetic twins. (50% chance within the same gender). And that would also be identical to the offspring from one crossing one grandparent on each side... Fortunately this doesn't happen!
Since men (typically) only have one X chromosome to start, the X passed in their sperm is identical to that of their somatic cells. So two sisters with the same parents will share one identical X from their father, but the second X from their mother will be different combinations of her two X's.
Edit to add: if genetic recombination didn't happen, then lots of siblings would end up as genetic twins. (50% chance within the same gender). And that would also be identical to the offspring from one crossing one grandparent on each side... Fortunately this doesn't happen!
"50% chance within the same gender"? What about all the other chromosomes? Wouldn't they have to match too?
I meant if genetic recombination didn't happen at all in organisms, just as an illustration. In reality all chromosomes, not just X, undergo recombination.
Whoops, yes, brain fart above. There are still 2^22 ways to arrange the other chromosomes passed in an egg or sperm.
Women require a man to contribute before they can give birth
You can convert female cells to sperm cells (using stem cells), so male is not required. Although, I believe the offspring can only be female.
There is a wrinkle, genetic imprinting.
You can put a woman's X chromosome in a sperm but it'll be labelled "from mum" and not work quite right.
See Prader Willi and Angleman syndrome for examples.
You can put a woman's X chromosome in a sperm but it'll be labelled "from mum" and not work quite right.
See Prader Willi and Angleman syndrome for examples.
This won't work. Male genomes are imprinted to form a placenta. For example, when embryos receive two sets of genes from a male and none from the female, they turn into molar pregnancies (a giant, aggressive placenta). Embryos receiving both set from a female and none from a male do not form a placenta and can't implant.
I think this will be the norm in the future: women can simply reproduce artificially without any injections from men, and their children will all be female. Men will quickly die out, and the world will probably be better off honestly (just look at who fills up the prisons, and who starts and fights in wars).
gillci(3)
I was thinking the same sort of things but my understanding was the sperm that carries
the determination of sex not the egg.
As soon as we figure out how to choose the sex of our children, we as a species are in serious trouble.
1984 - https://pubmed.ncbi.nlm.nih.gov/6541168/
> A laminar-flow fractionation method, developed primarily for removing dead sperm from human semen, was successfully modified to enrich X and Y sperm to 80% purity, and to characterize each enriched fraction for individual swimming behavior. Y-sperm fractions were rapidly detected by fluorescent cytogenetic staining. Subsequently, the degree of enrichment was quantitated with DNA extracted from each sperm fraction probed with a human male-specific recombinant DNA clone. In stationary fluid, X and Y sperm swam in circles with the same average speed. However, in a flowstream, X sperm shifted to a nearly straight path of movement in a significantly decreased angular velocity. This shift was four times more pronounced in X sperm than in Y sperm, especially after the initial transition from stationary fluid to flow. The velocity gradient across the flow axis was essential for separating X and Y sperm; uniform flow velocity did not separate them effectively.
AMA Journal of Ethics - Sex Selection for Family Balancing https://journalofethics.ama-assn.org/article/sex-selection-f...
> Currently, there are three available methods for sex selection. The first option is prefertilization sperm sorting using flow cytometry, which can provide a semen sample enriched with sperm that bear the desired sex chromosome. Its accuracy is in the 84-92 percent range, and it is not yet available in the US [6, 7]. At the opposite end of the spectrum, the most extreme form of sex selection occurs after conception in the form of elective termination of pregnancy if prenatal testing shows the sex of the fetus is the opposite of that desired. In certain regions of the world, such as India, such procedures are commonly performed, despite being illegal [8, 9].
> A laminar-flow fractionation method, developed primarily for removing dead sperm from human semen, was successfully modified to enrich X and Y sperm to 80% purity, and to characterize each enriched fraction for individual swimming behavior. Y-sperm fractions were rapidly detected by fluorescent cytogenetic staining. Subsequently, the degree of enrichment was quantitated with DNA extracted from each sperm fraction probed with a human male-specific recombinant DNA clone. In stationary fluid, X and Y sperm swam in circles with the same average speed. However, in a flowstream, X sperm shifted to a nearly straight path of movement in a significantly decreased angular velocity. This shift was four times more pronounced in X sperm than in Y sperm, especially after the initial transition from stationary fluid to flow. The velocity gradient across the flow axis was essential for separating X and Y sperm; uniform flow velocity did not separate them effectively.
AMA Journal of Ethics - Sex Selection for Family Balancing https://journalofethics.ama-assn.org/article/sex-selection-f...
> Currently, there are three available methods for sex selection. The first option is prefertilization sperm sorting using flow cytometry, which can provide a semen sample enriched with sperm that bear the desired sex chromosome. Its accuracy is in the 84-92 percent range, and it is not yet available in the US [6, 7]. At the opposite end of the spectrum, the most extreme form of sex selection occurs after conception in the form of elective termination of pregnancy if prenatal testing shows the sex of the fetus is the opposite of that desired. In certain regions of the world, such as India, such procedures are commonly performed, despite being illegal [8, 9].
The Ericsson method has been around since the 70s and works pretty well. ~70% chance of getting the sex you want. It works because the Y chromosome is a lot smaller than the X so Y sperm can swim faster.
We did that long ago - don’t feed the ones you don’t want.
That has been a possibility since the early 2000's. I read about it in New Scientist magazine.
koollman(2)
colpabar(6)
In a way, all cells are female, because DNA from sperm and egg is the software, but it always runs on female hardware (the egg).
This is also why "cloning dinosaurs" might be extremely difficult even if you found complete DNA, you lack compatible enough hardware to run that DNA on.
This is also why "cloning dinosaurs" might be extremely difficult even if you found complete DNA, you lack compatible enough hardware to run that DNA on.
Would the DNA not describe the cell it belongs in?
Not completely. For example mitochondrial DNA is totally separate from regular DNA, and it's passed exclusively mother to offspring.
It's the old bootstrapping problem - how do you get a running C compiler from code if you don't already have a running C compiler?
There is no example in nature where you get a fully functional cell starting exclusively from DNA.
It's the old bootstrapping problem - how do you get a running C compiler from code if you don't already have a running C compiler?
There is no example in nature where you get a fully functional cell starting exclusively from DNA.
"it's passed exclusively mother to offspring"
As in most absolute statements, this may not be completely true. Sperm has some mitochondria that likely is incorporated into the zygote.[1]
[1] https://en.wikipedia.org/wiki/Paternal_mtDNA_transmission
As in most absolute statements, this may not be completely true. Sperm has some mitochondria that likely is incorporated into the zygote.[1]
[1] https://en.wikipedia.org/wiki/Paternal_mtDNA_transmission
Afaik the mitochondria of the sperm cell is located in the tail to power it which then gets detached from the head just after it has borrowed into the egg ???.
From the Wikipedia page (read the original source for details):
The controversy about human paternal leakage was summed up in the 1996 study Misconceptions about mitochondria and mammalian fertilization: Implications for theories on human evolution, which was peer-reviewed and printed in Proceedings of the National Academy of Sciences.[15] According to the study's abstract:
The controversy about human paternal leakage was summed up in the 1996 study Misconceptions about mitochondria and mammalian fertilization: Implications for theories on human evolution, which was peer-reviewed and printed in Proceedings of the National Academy of Sciences.[15] According to the study's abstract:
In vertebrates, inheritance of mitochondria is thought to be predominantly maternal, and mitochondrial DNA analysis has become a standard taxonomic tool. In accordance with the prevailing view of strict maternal inheritance, many sources assert that during fertilization, the sperm tail, with its mitochondria, gets excluded from the embryo. This is incorrect. In the majority of mammals—including humans—the midpiece mitochondria can be identified in the embryo even though their ultimate fate is unknown. The "missing mitochondria" story seems to have survived—and proliferated—unchallenged in a time of contention between hypotheses of human origins, because it supports the "African Eve" model of recent radiation of Homo sapiens out of Africa.