I almost asked

Q: Which came first, the chicken or the egg?
A: I don't know. Why don't you ask the rooster?

Sitting in class this morning (Molecular Foundations of Medicine) I was tempted to ask this question. Well, not really this question, but the analog of it as it applies to the basis of life. We were learning about transcription and translation, basically how DNA codes for RNA codes for proteins. There are a helluva lot of "helper" proteins involved: transporters, initiation and regulation factors, etc.

So naturally, I wondered how, with all these helper proteins required for proper protein synthesis, anything ever got started? Think about it: RNA is the template for proteins, but proteins help construct amino acid chains based on the RNA sequence, that eventually fold into proteins.

Luckily, I didn't have to ask. The lecturer offhandedly mentioned a current theory that early forms of life used RNA as an enzyme, doing many of the duties that proteins do now. Evidence supporting this is that ribosomes still have enzymatic rRNA, a probably evolutionary "leftover" from these earlier mechanisms.

So I guess the egg came first.