Lyonization vs Imprinting

[SKaminski]

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I'm having trouble understanding the difference between these two (lyonization and imprinting). It seems like both of them are the random inactivation (via condensation) of chromosomes.

What am i missing?

 

[worldbeater]

This doesn't directly answer your question, but from what I remember, imprinting is associated with Prader Willi/Angelman's Syndrome (deletion of chromosome 15 - World Q x 2), lyonization is vaguely familiar don't remember what it's for. That may help.

 

[dorster]

Im pretty sure its only called lyonization when the entire X chromosome is inactivated by condensation (like forming the barr body) and if this randomly happens in a way that a female can express the X linked recessive disorder phenotype. Whereas imprinting is when a specific gene or group of genes is silenced by methylation. It can happen on any chromosome and actually happens normally. The example is with Angelman Syndrome where the maternal gene is normally the only active copy and the paternal gene is normally the methylated (inactive) copy. So when the maternal gets deleted or mutated its the only active copy so the child will have angelman. Methylation is gene silencing, not an entire chromosome and it doesn't have to occur on X chromosome.

 

[Xavyer]

Lyonization is inactivation of one of the X chromosomes in females. Since females have 2 X chromosomes, having both active would be redundant and cause problems. One of the chromosomes is inactivated (the one that is selected is random).

Genomic imprinting is an epigenetic phenomenon that has to do with DNA methylation/silencing. It occurs when either the dad or mom's allele is expressed. That is, if the paternal allele is imprinted (silenced), only mom's is expressed. If the maternal allele is imprinted, dad's is expressed.

 

[recycledpaper]

Im pretty sure its only called lyonization when the entire X chromosome is inactivated by condensation (like forming the barr body) and if this randomly happens in a way that a female can express the X linked recessive disorder phenotype. Whereas imprinting is when a specific gene or group of genes is silenced by methylation. It can happen on any chromosome and actually happens normally. The example is with Angelman Syndrome where the maternal gene is normally the only active copy and the paternal gene is normally the methylated (inactive) copy. So when the maternal gets deleted or mutated its the only active copy so the child will have angelman. Methylation is gene silencing, not an entire chromosome and it doesn't have to occur on X chromosome.

Edit

 

[dorster]

Angelman is maternal deletion with PATERNAL silencing. Just correcting you for anyone reading your answer.

lol isn't that what i said? not trying to be rude but i did say the maternal gene is NORMALLY the active copy. The Paternal gene is normally methylated (aka silenced). We're saying the same thing.

 

[recycledpaper]

You are 100% right. I must've not had my morning coffee - my apologies!

 

[dorster]

You are 100% right. I must've not had my morning coffee - my apologies!

haha no worries! probably too much time starting at the screen (or maybe thats just me i feel like I'm going blind)