Feature: Origins of life

David Penny.

This feature appeared in the November/December 2009 issue of Australian Life Scientist. To subscribe to the magazine, go here.

Late on the morning of September 28, 1969, a piece of space rock sonic-boomed across the south-eastern Australia sky and broke up, scattering chunks of speckled, black rock across the rural landscape near the Victorian hamlet of Murchison. The famed Murchison meteorite, a rare carbonaceous chondrite, delivered to Earth a soup of organic ingredients, including proteogenic amino acids like glycine, alanine, and glutamic acid and uracil, one of the four bases that form RNA.

It’s from building blocks such as these that scientists, like David Penny, Professor of Theoretical Biology at Massey University’s Institute of Molecular Biosciences in Palmerston North, in New Zealand, believe led to the first self-replicating RNA molecules, They, in turn, begat all life on Earth. Proteins and DNA came later, when chance and natural selection colluded to add a second, template strand to the primal life code, greatly enhancing its stability and fidelity.

So while DNA has occupied centre stage in biological research for almost half a century, a research revolution in the past decade has made it clear that RNA rules. The true nature of the vast tracts of so-called ‘junk DNA’ within and between genes is revealed: many code for a host of small RNA molecules which collectively drive and coordinate the intricate machinery of the genome.

But as Penny observes, RNA “didn’t pop out of nowhere”. How, and under what physical conditions, did simple RNA oligonucleotides bootstrap themselves through the evolutionary process leading to complex, self- replicating RNA molecules with catalytic activity?

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