Jan 11 2010
The Non-Line Between Life and Not-Life
People fond of simple answers would prefer if there were a clean line in the sand, so to speak, between life and non-life–between what we categorize as “alive” and what call “inanimate.” But the more you examine the boundary, and refine the definition that creates the boundary, you encounter many problems. Like the virus. And, more recently, the prion.
An article I found over at ScienceDaily illustrates the point. The ground-breaking news:
…prions, bits of infectious protein devoid of DNA or RNA that can cause fatal neurodegenerative disease, are capable of Darwinian evolution.
Prions evolve?! If not ground-breaking, this news is at least sand-sweeping. Where’s that clean line between life and not?
Here are some important points drawn from the article:
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Infectious prions (short for proteinaceous infectious particles) are associated with some 20 different diseases in humans and animals, including mad cow disease and a rare human form, Creutzfeldt-Jakob disease.
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Prions have the ability to reproduce, despite the fact that they contain no nucleic acid genome.
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In viruses, mutation is linked to changes in nucleic acid sequence that leads to resistance. Now, this adaptability has moved one level down — to prions and protein folding — and it’s clear that you do not need nucleic acid for the process of evolution.”
As a final exclamation point, the tail section of the article carries this sub-head: “Quasi-Species.”
If there is a line in the sand, it is quite quasi.
Prions are fascinating things. My first lecturer used to call them ‘vampire proteins’ to help explain their behaviour, so perhaps we could call them ‘undead’? Thanks for the article link.