Explaining Ageing

 Warning: this is one of those sciencey things I warned you about a few months ago (the first strangely!)

 This is just WAY cool in my opinion - since learning about DNA and its purposes in high school biology, I have wondered how it is related to people growing older.  The DNA is the same right?  Wrong! :O  Scientists have been comparing the DNA of babies to the DNA of the lucky that live to 100+.  And guess what?!?  There are differences!  Not in what DNA codes for but the methylation.

 There is this thing called epigenetics that looks at how your DNA is different on the outside (e.g. methylation) and not what it codes for.  This external modification changes the expression of genes in your cells!  Methylation is the addition of a methyl group (-CH3) to the sugar backbone of the DNA.  External DNA modification changes how DNA is stored and how easily proteins that read and copy it can access it.  It has been discovered that as you age, you lose 7% of the methylation (starting at 80% of sites down to 73%) which leads to altered expression.  There are many things that can effect the amount of DNA that is methylated (or externally modified), some of which can come from your grandparents and could be related to when they may have experienced famine! (google it! I dare you - it's pretty cool, and PBS|Nova has a special about Epigenetics that is good)

From: http://en.wikipedia.org/wiki/Epigenetics

If you are so scientifically inclined, here is the article about the recent discovery: Epigenomic Differences between Newborns and Centenarians Provide New Insights into Ageing