3 ms·

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 cons

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 https://jbiol.biomedcentral.com/articles/10.1186/jbiol95

hinkley 4y ago
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 4y ago
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shagie 4y ago
> > 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 https://en.wikipedia.org/wiki/X-inactivation ) even has a picture of a tortoiseshell cat.
anon291 4y ago
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.

hinkley 4y ago

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 4y ago

[deleted]

shagie 4y ago

> > 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 https://en.wikipedia.org/wiki/X-inactivation ) even has a picture of a tortoiseshell cat.

anon291 4y ago

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.