5 ms·

The article doesn't touch on X-chromosome Inactivation[1] which makes all female animals mosaic. Though in the specific case in the article SCN5A isn't on the X

The article doesn't touch on X-chromosome Inactivation[1] which makes all female animals mosaic. Though in the specific case in the article SCN5A isn't on the X[2]. 1: https://en.wikipedia.org/wiki/X-inactivation https://en.wikipedia.org/wiki/X-inactivation 2: https://ghr.nlm.nih.gov/gene/SCN5A#location https://ghr.nlm.nih.gov/gene/SCN5A#location

tamcap 8y ago
X-chromosome inactivation is a type of an epigenetic change. It is one of many that happen throughout the body - I would say there are very few cells in our bodies that have the same epigenetic markup. We've known about this for a while. The article discusses genetic post-meiotic changes that propagate differentially through the body. We knew it happened for a while now too, but it was always presented as a curiosity or an anomaly. We are now learning that it is much more common than we anticipated. Like presented in the article, it might actually explain some clinical phenotypes as well.
- hinkley 8y ago
  Don’t organs, limbs, spots and stripes form in a fetus due to epigenetics?
  - kyberias 8y ago
    No, they form because of genetics: differential gene regulation.
  - rubatuga 8y ago
    You're not wrong, it's a mixture of epigenetic changes, and local environment changes. As a cell differentiates, it definitely changes its epigenome. These changes are also mediated by cell-cell interactions, and other morphogenic proteins, for example, the SHH gene: https://en.wikipedia.org/wiki/Sonic_hedgehog https://en.wikipedia.org/wiki/Sonic_hedgehog
- himom 8y ago
  Male birth order-linked gayness probability is epigenetics in the mother IIRC.
  - gowld 8y ago
    Interesting. https://en.wikipedia.org/wiki/Fraternal_birth_order_and_male_sexual_orientation#Empirical_findings https://en.wikipedia.org/wiki/Fraternal_birth_order_and_male... "Secondly, the fraternal birth order effect operates through a biological mechanism during prenatal life, not during childhood or adolescence. Direct evidence for this is the fact that the fraternal birth order effect has been found even in males not raised with their biological brothers – it has been determined that biological brothers increase the odds of homosexuality in later-born males even if they were reared in different households, whereas non-biological siblings, such as step-brothers or adopted brothers, have no effect on male sexual orientation." That is consistency with a "kin-selection" theory of homosexuality, that within a family, evolutionary factors favor having partially non-reproductive members in a family (perhaps because in a family with two males, on average, the total reproductive fitness is greater where there is one father and one uncle, not two fathers)
    - toasterlovin 8y ago
      The math is pretty clear: the chances that homosexuality, as a trait in and of itself, is selected for is highly unlikely. A gay person would have to result in their siblings having 2x as many children as they would have themselves, which is possible, but a really steep hill to climb. The explanation that makes much more sense to me is that homosexuality is an occasional side effect of something else which is highly adaptive to non-gay siblings who possess it.
      - notabee 8y ago
        Humans have many traits that seem to support survival at the tribal level, and having a spectrum of homosexual and heterosexual individuals could well have supported child rearing or reduced divisive competition. Just look at bonobos.
gus_massa 8y ago
> which makes all female animals mosaic Nitpicking: We have the XY system but birds have the ZW system where the male birds have the chromosomes ZZ and the female birds have the chromosomes ZW (More info: https://en.wikipedia.org/wiki/Sex-determination_system https://en.wikipedia.org/wiki/Sex-determination_system ) I still can't find out if in this case the male birds have a random inactive Z and are mosaic. I guess that there is something similar, but I'm not sure.
- blacksmith_tb 8y ago
  Thanks, I was just lifting that from the wiki article (arthropods are animals too, and they don't have XY chromosomes either, of course). Those crazy feathered therapods! Plus, nucleated red blood cells[1]. 1: http://www.askabiologist.org.uk/answers/viewtopic.php?id=9296 http://www.askabiologist.org.uk/answers/viewtopic.php?id=929...
SamReidHughes 8y ago
IIRC not marsupials, which get the same chromosome chosen over the entire body.

tamcap 8y ago

X-chromosome inactivation is a type of an epigenetic change. It is one of many that happen throughout the body - I would say there are very few cells in our bodies that have the same epigenetic markup. We've known about this for a while. The article discusses genetic post-meiotic changes that propagate differentially through the body. We knew it happened for a while now too, but it was always presented as a curiosity or an anomaly. We are now learning that it is much more common than we anticipated. Like presented in the article, it might actually explain some clinical phenotypes as well.

hinkley 8y ago
Don’t organs, limbs, spots and stripes form in a fetus due to epigenetics?
- kyberias 8y ago
  No, they form because of genetics: differential gene regulation.
- rubatuga 8y ago
  You're not wrong, it's a mixture of epigenetic changes, and local environment changes. As a cell differentiates, it definitely changes its epigenome. These changes are also mediated by cell-cell interactions, and other morphogenic proteins, for example, the SHH gene: https://en.wikipedia.org/wiki/Sonic_hedgehog https://en.wikipedia.org/wiki/Sonic_hedgehog
himom 8y ago
Male birth order-linked gayness probability is epigenetics in the mother IIRC.
- gowld 8y ago
  Interesting. https://en.wikipedia.org/wiki/Fraternal_birth_order_and_male_sexual_orientation#Empirical_findings https://en.wikipedia.org/wiki/Fraternal_birth_order_and_male... "Secondly, the fraternal birth order effect operates through a biological mechanism during prenatal life, not during childhood or adolescence. Direct evidence for this is the fact that the fraternal birth order effect has been found even in males not raised with their biological brothers – it has been determined that biological brothers increase the odds of homosexuality in later-born males even if they were reared in different households, whereas non-biological siblings, such as step-brothers or adopted brothers, have no effect on male sexual orientation." That is consistency with a "kin-selection" theory of homosexuality, that within a family, evolutionary factors favor having partially non-reproductive members in a family (perhaps because in a family with two males, on average, the total reproductive fitness is greater where there is one father and one uncle, not two fathers)
  - toasterlovin 8y ago
    The math is pretty clear: the chances that homosexuality, as a trait in and of itself, is selected for is highly unlikely. A gay person would have to result in their siblings having 2x as many children as they would have themselves, which is possible, but a really steep hill to climb. The explanation that makes much more sense to me is that homosexuality is an occasional side effect of something else which is highly adaptive to non-gay siblings who possess it.
    - notabee 8y ago
      Humans have many traits that seem to support survival at the tribal level, and having a spectrum of homosexual and heterosexual individuals could well have supported child rearing or reduced divisive competition. Just look at bonobos.

gus_massa 8y ago

> which makes all female animals mosaic Nitpicking: We have the XY system but birds have the ZW system where the male birds have the chromosomes ZZ and the female birds have the chromosomes ZW (More info: https://en.wikipedia.org/wiki/Sex-determination_system https://en.wikipedia.org/wiki/Sex-determination_system ) I still can't find out if in this case the male birds have a random inactive Z and are mosaic. I guess that there is something similar, but I'm not sure.

blacksmith_tb 8y ago
Thanks, I was just lifting that from the wiki article (arthropods are animals too, and they don't have XY chromosomes either, of course). Those crazy feathered therapods! Plus, nucleated red blood cells[1]. 1: http://www.askabiologist.org.uk/answers/viewtopic.php?id=9296 http://www.askabiologist.org.uk/answers/viewtopic.php?id=929...

SamReidHughes 8y ago

IIRC not marsupials, which get the same chromosome chosen over the entire body.