Friday, March 16, 2012

Mitochondria

My cousin Tibor and I (we’re of the same age) were exchanging, with help from HP Photosmart, very yellowing family-tree information that reaches its frail bony fingers all the way back to 1645 to an ancestor of ours called Peter—indeed bemoaning that the finger doesn’t reach all the way back to 1470, when an even older male forebear, according to a coat of arms, gave rise to the famed Darnay name—only, alas, it was then still just Dorner. Men’s names everywhere, in heavy ink, the progenitating ladies sort of sidelined with less obvious emphasis. But this is a patriarchal time—and has been since somebody way, way back in the pre-BC era, as it were, decided that things really pend from men.

Contrarian that I am, naturally I thought of mitochondria. These are, in a way, my favorite organelles, found in eukaryotic (read “advanced”) cells. They manufacture ATP (adenosine triphosphate), the fuel of chemical energy. The mighty mitochondria, therefore, are the power plants inside our cells. Now nature knows best—and knows what really is important. It’s about energy, stupid, not male descent. And nature also knows that women are, as it were, slightly better designed than men. For this reason the mitochondria in our bodies—and they have their own DNA—all come from the female. To be sure, sperm cells bring mitochondria from the male parent, but in the embryo only the little power-plants from the female egg are reproduced. What happens is a kind of culling. During the formation of the embryo, the mitochondria introduced by sperm are marked by a regulatory protein called ubiquitin (the name deriving from ubiquitous, because they are). The presence of this marker means that the unfortunately tagged mitochondria from the father’s side are recycled into proteins—not used to make ATP. If they lived in a male, they are suspect; the male metabolism probably messed them up by recombination and such like shenanigans. The female rules.

For this reason a really, really long look back into the very dawns of time makes use of tracing mitochondrial DNA backward. A book that reports on  such efforts is Bryan Sykes’ The Seven Daughters of Eve. Sykes is a professor of human genetics. The book, alas, is only mildly fascinating. Humanity as we know it can be traced back to seven females and is also, incidentally, useful for tracing the geographic origins of various population groups.

The most intriguing aspect of mitochondria, for me, is that they are clearly immigrants to the eukaryotic cell—acquired along the line to provide a sophisticated functionality. That is why they have their own DNA. All that’s left now of their once glorious origins is the power plant they’d originally built. Which, in turn, resonates with our family’s history too. We were German immigrants who brought hi-tech to the backward regions of Hungary—iron-working skills that one branch of our family, recorded on those yellowing sheets, still practiced in my grandparents’ generation.

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