Evolution, Genes, and Disease

…McInerney and his colleague David Alvarez-Ponce surveyed the human genome and separated the genes into three groups based on taxonomic molecular signatures. One set contained genes inherited from our eubacterial ancestor, one from the archaebacterial ancestor and one held genes unique to eukaryotes. (Fingernail protein, for example, has no ancient doppelganger.)

“They’ve found an imprint of this original symbiosis remaining after 1.5 billion years,” said Bill Martin, an endosymbiosis researcher at Heinrich-Heine-Universität Düsseldorf, in Germany and editor of the journal publishing the study. “This is a brilliant discovery. You would have thought someone would have noticed this, but nobody ever did.”

Beyond that, McInerney and Alvarez-Ponce found gene communities hold different functions. Archaebacterial genes are usually responsible for information processing, and appear to be especially important. They’ve accumulated fewer DNA mutations than eubacterial genes, suggesting that changes are more likely to have major consequences.

Eubacterial genes tended to be involved in biochemical processes. They were also more likely to be implicated in heritable human disease risk.

That more-important archaebacterial genes are found less frequently in disease might seem counterintuitive, but McInerney thinks the imbalance might exist because archaebacterial gene mutations often prevent organisms from developing at all.

This just shows how it is absolutely impossible for an organism to escape its evolutionary past. It also has implications for what makes us, us. From this it appears as if our core functions are the result of archaebacteria, so to understand human chemistry we may need to focus a bit more on their chemistry.

The only real issue I had with the article was this:

While some scientists think prokaryotes evolved directly into eukaryotes, others think it required a merger, with two cells — one archaebacteria and one eubacteria — joining at some prehistoric point to make a cell capable of complex internal structures.

I’d like to know which scientists think it wasn’t the result of endosymbiosis. I would have thought the whole bit about mitochondrial DNA resembling bacterial DNA would be a pretty clear giveaway there was some fusion event. Especially when you consider the membrane in our mitocondria has the same proteins as the cell membrane in eubacteria.

I’m sure you could find some who disagree, but I can find a scientist who says pretty much anything. And this finding here actually makes it even clearer as there are genes within us with clear eubacterial origin and genes with clear archaebacterial origin. There had to be some sort of fusion even at some point in our evolutionary past.