On Fri, Aug 9, 2013 at 9:43 PM, Chris de Morsella <cdemorse...@yahoo.com>wrote:

> some feel Epigenetics should only refer to the actual molecular
> mechanisms (such as DNA methylation and histone modification) that alter
> the underlying gene expression; I find this restrictive and use epigenetics
> to also describe inheritance of changes in the expression of genes. There
> appears to be increasing evidence that points to epigenetic inheritance

Yes, but that also means that epigenetic inheritance is fundamentally less
important than the traditional sort. If you don't have the gene then you
just don't have it and that's all there is to it, but if you have the gene
but it's not expressed because of one simple methyl group then one of your
sperm could lack those 4 atoms (CH3) and your offspring, or his offspring,
could inherit the fully functional complex gene even if there was no sign
of its expression in you.

 > maternal nicotine exposure during pregnancy is linked to asthma in the
third generation in disease models. [...]
Isn’t this essentially describing a Lamarckian process?

I don't dispute the existence of epigenetic changes even if it's far less
important than Mendelian inheritance, but where is the acquired
characteristic? If exposure to nicotine led to nicotine tolerance in the
parent and the offspring then it would give some support to the inheritance
of acquired characteristics, but instead you've just got asthma. It's not
news that some chemicals increase the rate of mutation. And besides, you
need a lot more than the inheritance of acquired characteristics for
Lamarckian evolution to work, you need a way to separate the good acquired
characteristics from the bad (asthma is bad), and only Darwinian natural
selection can do that.

  John K Clark

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