Lefebvre on epigenetics
Nov. 10th, 2008 01:00 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
guslThis Saturday I skipped Grisman to see Louis Lefebvre talk about epigenetics. Being a total layman, I found it very accessible and enjoyable, even if I was somewhat puzzled about the basic facts.
Rough summary / questions:
* epigenetics can mean many different things. Etymologically, "epi-" is like "beyond".
* one kind is CG-methylation (aka "Ç" if you think of methyl as cedille) which renders genes inactive.
It is a kind of statefulness that can get passed on during transcription (due to methyl's tendency to cross the DNA), but apparently not meiosis(?), related to inactivation of genes (IIRC, also X-inactivation in females)
* in the zygote, the methylation state gets reset (methyl goes away?); human cloning is a bad idea because this resetting doesn't happen, leading to severe malformations. Of course, this raises the question of how methylation state could possibly be inheritable.
* diseased genes can be passed for many generations, e.g. down a paternal line, and only manifest themselves once they pass this gene on to a daughter, who passes it on to a child, who shows the diseased phenotype (or vice-versa: invisible down a maternal line until they have a son who has a child). I wonder what kind of mechanism could explain this.
* I found it a bit surprising that the zygote is formed before the two gametes' DNA get together (duh!), meaning there's no attempt to check how well this individual sperm matches this individual egg. This lack of selection implies that the zygotes formed are "really" "random". Though I wonder if sperm DNA is related to sperm phenotype, leading to a selection there.
* You can observe methylation state as a green light, using rats bred with genes for bioluminescence! There were two types of females (presumably, due to them having two Xs), one showing no light, one showing a dim green light. All males showed a bright green light. I don't understand this.
* The presenter himself was colorblind. So was his father. But of a very different type, inherited from his mother.
* Someone asked if epigenetics was bringing back the idea of Lamarckian inheritance. I didn't understand his answer.
Sigal and her former evolutionary psych professor (Cauffrey?) were there, and we had an interesting geeky conversation (even if largely beyond me, due to my lack of background).
Rough summary / questions:
* epigenetics can mean many different things. Etymologically, "epi-" is like "beyond".
* one kind is CG-methylation (aka "Ç" if you think of methyl as cedille) which renders genes inactive.
It is a kind of statefulness that can get passed on during transcription (due to methyl's tendency to cross the DNA), but apparently not meiosis(?), related to inactivation of genes (IIRC, also X-inactivation in females)
* in the zygote, the methylation state gets reset (methyl goes away?); human cloning is a bad idea because this resetting doesn't happen, leading to severe malformations. Of course, this raises the question of how methylation state could possibly be inheritable.
* diseased genes can be passed for many generations, e.g. down a paternal line, and only manifest themselves once they pass this gene on to a daughter, who passes it on to a child, who shows the diseased phenotype (or vice-versa: invisible down a maternal line until they have a son who has a child). I wonder what kind of mechanism could explain this.
* I found it a bit surprising that the zygote is formed before the two gametes' DNA get together (duh!), meaning there's no attempt to check how well this individual sperm matches this individual egg. This lack of selection implies that the zygotes formed are "really" "random". Though I wonder if sperm DNA is related to sperm phenotype, leading to a selection there.
* You can observe methylation state as a green light, using rats bred with genes for bioluminescence! There were two types of females (presumably, due to them having two Xs), one showing no light, one showing a dim green light. All males showed a bright green light. I don't understand this.
* The presenter himself was colorblind. So was his father. But of a very different type, inherited from his mother.
* Someone asked if epigenetics was bringing back the idea of Lamarckian inheritance. I didn't understand his answer.
Sigal and her former evolutionary psych professor (Cauffrey?) were there, and we had an interesting geeky conversation (even if largely beyond me, due to my lack of background).