Monday, September 27, 2010
Life from an RNA World: The Ancestor Within
As you might guess, this is not a piece of whimsy. It's a scientist's attempt to explain what the RNA world might have been like. ("When RNA ruled the earth!") It's aimed at nonprofessional scientists, by which I mean people who like science but don't necessarily know how to read scientific papers or have the chemistry and/or molecular biology background necessary to understand the material. As a result, about half the book is background, which was a nice little review for me.
However, I don't know if it would be so easy for someone without a higher degree in a life science to understand. The author tries too hard not to use scientific jargon, and as a result uses vague words that only hint at what he's trying to explain. Instead of saying "DNA", he'd say something like "the molecule that holds the universal code for life". The words often get in the way.
But once I sorted through that maze, there was some interesting material. I especially enjoyed the chapter that describes all the different types of RNA. Most textbooks focus on the major three: mRNA (messenger), tRNA (transfer), and rRNA (ribosomal). But there are many more noncoding RNAs (ncRNAs, basically everything that isn't mRNA) with specific functions, and many of which were only recently discovered. The functions of many are still unknown, but it's a very good description of these RNA types.
Then the author goes into what would be required in an RNA world (an RNA with the ability to make new RNA strands using an existing RNA strand as a template), and experiments that try to determine whether this molecule could exist. Because I'm more interested in what it might look like and how it might function than whether it's possible, this chapter didn't quite satisfy me. I'm also interested in how such a molecule might originate and how it would be selected (in the RNA world, not in the laboratory), and the book didn't cover that very well either.
Finally, how did the RNA world transform into the world of cells? The evolution of the genetic code is still a big question, but evidence of how that might have occurred is also presented. It's starting to sound feasible, but it's not a whole story.
What I'm looking for, I guess, is more of a narrative of how simple molecules could form a replicator and how that replicator might have gained fidelity, and how this may have provided the propagation of RNAs with other functions, and finally how a ribocyte might have discovered protein synthesis, and how protein synthesis might be directed by RNA or DNA code. Finally, what did our last common ancestor look like?
This book is a good start, for sure. I'll probably come back to it in the future, so I'm glad I actually bought it. It's up to date and interesting. But at the end of each chapter is a list of references to scientific papers that should be even more insightful. The trail continues.