The DNA/gene/protein system has two distinct features. First, the DNA molecule is a “double helix” composed of two compimentary “single helix” strands that bond together, protecting the information they contain by presenting a stable phosphate-sugar backbone to the harsh chemical world around them. Second, DNA’s only job is to store information. Transforming DNA’s information into the actual structure of organisms is the job of tens of thousands of different proteins, each of which has a unique three-dimensional shape that lets it work on other proteins and other chemicals like a bunch of snap-together legos.

Clever system – and too complicated to set up full-blown and operational from inorganic starting chemicals at the dawn of life. Instead, consider RNA. It’s a cousin of DNA that can store “information” in the form of a single rather than a double strand that doesn’t form a helix at all. Instead, it can also bond with itself at various points to produce three-dimensional structures that can exhibit the chemical activity of proteins. So primitive RNA can fill both roles of modern DNA and proteins in one single package. Eons ago, at the dawn of life, that’s just what RNA did – somehow – and created simple cells that evolved into the DNA/protein based cells around us today. Those rambunctious DNA newcomers proceeded to obliterate the earlier RNA based cells from whence they sprung, which are now extinct, and “enslave” RNA to a “mere” supporting role in modern cells.

Work to understand the potential of RNA continues, with the latest progress reported at the recent Denver AAAS meeting. Erik Schultes of MIT-Whitehead reported on an experiment in which a particular sequence of RNA bases could, by altering one base at a time, take on rather quickly the identity of either of two very different ribozymes (RNA molecules that can catalyze reactions) with two very different functions: one for cleavage (breaking RNA/DNA protein strands apart) and one for ligation (gluing two of those strands together). Schultes’ work thus identifies a particular RNA strand that, if developed by chance via pre-biological processes on ancient Earth, would automatically form a type of “tool-kit” necessary to kickstart the evolution of more advanced life forms.

In other work described by Tom Siegfried of The Dallas Morning News, researcher Ranjan Mukhopadhyay of NEC Laboratories in New Jersey announced his discovery that a RNA sequence with its 4-base chemical code folds more predictably and stably than would hypothetical RNA sequences based on a two-base or six-base “alphabet”. This explains why life is a “four letter word” with DNA and RNA using only four chemicals to store information instead of some other number.

Finally, in other theoretical work, Ralf Bundschuh of Ohio State and Terence Hwa of UC-San Diego have shown that RNA can exhibit several different “phases,” just as water can exist as water, ice and steam. In the case of RNA, Bundschuh showed mathematically RNA could exist in a normal, glassy, molten, or denatured phase. At low temperatures, for instance, in the “glassy” phase, a given RNA sequence can get stuck in a random structure. At higher temperatures, RNA can assume a more flexible “molten” state, in which it is free to fold into a variety of different shapes – including some that are perhaps conducive to the formation of life.