So, for a quick answer … there is no "strand" that tells a cell to die. (Remeber there are only 2 antiparallel strands of DNA).

However, regions within DNA (or in genes) can make a cell/organism more suceptible to death. For example … cancer is a genetic disese. Cancer is caused by mutations in DNA that generally promote uncontrolled growth (of a cell type that doesn’t ‘work-right’) So, if you have lung cancer.. you’d have have 1 cell that divids THOUSANDS of times… However, these THOUSAND cells don’t work correctly (they don’t exchange carbon dioxide for oxygen). So what happens? THese cells just overgrow the normal cells and eventually there aren’t enough ‘normal’ cells to breathe-with and keep you alive. … and then you die.

So esentially the mutant (cancerous) gene doesn’t exactly ‘tell’ the cell/organism when to exactly to die … but instead makes a organism more likely to die, than to live.

Of course alot of studies have investigated genes that cause againg. But, scientist have not been able to exactly identify genes that promote life in humans yet. (although they have an idea how to increase life-span in flies).

well, this is just a short and simplified explanation….. hope it helps

actually they are working with fruit flies, which live for several weeks i think. and they are doing it in order to understand how to do it in humans in the future.
PS: aging is also caused by the build-up of mitochondrial mutations

In fact there are evidences that telomeres (the "ends" of the chromosomes) may be related to the cells survival… they get smaller every new cell division untill a certain point at which the cell dies. Some cencerous cells have large amounts of an enzyme (telomerase) which inhibits this size decrease.
(i’m not a specialist though)

The way to extend life span in flies (drosphila melanogaster)? Simple Calorie restriction and not allowing them to mate(ehem… lifelong abstinence!).

yes… both situations suck! And i’m not willing to do either… I’ll just take my normal humanly life span (thank you very much!)

And yes!!! Mitochondrial mutations are very important in the aging process (there was and AWESOME AWESOME AWESOME paper out in science last year… or so about this)

As far as the telomere thing, well that’s being debated, some studies support the telomere shortening thing BUT others say that there may be a correlation but it’s not exactly direct. (that’s not my field… so I don’t know which side to support!)

kool stuff!
– KIM