The causes of aging (gerontology) has been a very active research area lately with a great deal of theoretical and experimental progress in elucidating several contributing causes at the molecular level, although the work is still in an early stage and no remedies are near ready for clinical application. While all these causes probably make some contribution to the aging process, the one that most researchers seam to favor as the major contributor is chemical disruption of the mitochondrial genome due to the corrosive effect of reactive oxygen species ROS.
Don't freak out just yet. I'll try to explain some of this before I get to my question. The mitochondria are small organelles that we have in each of our cells and their primary function is to process sugar to produce energy for all of the other cellular processes. These organelles have their own genome consisting of several copies of a circular DNA molecule that codes for 13 proteins and 24 RNA molecules. The process of producing high energy ATP molecules from sugar that the mitochondria carry out involves several very reactive chemical intermediaries that slowly degrade the mitochondria 'innards' including its genome. The mitochondria are constantly reproducing and dying out, and when the cell they are in duplicates to make new cells, it doubles the number of its mitochondria to supply both cells. The DNA errors mentioned above are propagated to the new mitochondria and cells. There is strong experimental evidence that this continuous propagated degradation over the years is the major cause of aging. We get old because our mitochondria get old.
On to my question. We get our mitochondria from our mothers. All the mitochondria in all the cells of our entire body are descendants of the mitochondria that were in the egg cell in our mothers ovaries before it was even fertilized. Our fathers sperm did not contribute any mitochondria. Each of our mothers produced the 200,000 to 300,000 eggs that she has in her ovaries during that last stages of her gestation, i. e., during the last couple of months that she was in her mother's (grandma's) womb. Female mammals are born with all their eggs already produced and waiting in the ovaries until the female reaches sexual maturity. (This has some fascinating implications for divine conceptions, but thats outside the scope of this thread.) Those eggs in her ovaries are of course derived from the fertilized egg that produced her in her mother's womb, so that all of our mitochondria also come from our maternal grandmother, and so on back to some first female homo sapien.
Now I really am getting to my question. Since we are typically born when our mothers are about 20 years old, and that egg with its original load of mitochondria has been sitting patiently in mama's ovary for that twenty years, why aren't these mitochondria 20 years old with 20 years of ROS induced degradation? In fact, these mitochondria were reproduced from some of grandmas already 20 year old mitochondria, which were produced from some of great grand-mama's....etc, etc. I. e., this long chain of females - about 10,000 in homo sapiens 200,000 year history, has been reproducing mitochondria for all that time and just passing them from body to body. Before conception, the eggs really aren't doing too much and probably are not very chemically active, but they are alive and must be undergoing some level of metabolism, so their mitochondria must be active and producing some level of ROSs. So, why aren't we 200,000 years old when we are born? (or at least a lot more aged and decrepit that a new born baby?)
Is there some sort of mitochondria genome resetting mechanism, and if so, can this be exploited to ameliorate aging? Or is there something I just don't understand about the reproductive process? (My wife votes for the second option.)
Regards, AnInGe
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I've heard that the downside of immortality is that the second trillion years can drag on a bit.
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