According to the dogma du jour, the progenote (last common ancestor of
all surviving living things) used DNA as its genetic material and
proteins for most of its catalytic agents. That suggests that all
surviving RNA-containing catalytic agents have pre-progenote origins.
In particular, the intron splicing systems seem to all involve
ribozymes, thus suggesting that introns were present in the progenote.
On the other hand, both the eubacteria and the achaeobacteria lack
introns, whereas the eukaryotes have introns, which would suggest that
introns arose only in the early ancestors of the eukaryotes.
Does anybody have a fix on the current thinking in these areas?
Dale Worley Dept. of Math., MIT drw at math.mit.edu
If you ask an engineer, 'What is 3 times 4?' he does not answer at
once. He fishes a contraption known as a slide-rule out of his
pocket, fiddles with it for a moment, and then says, 'Oh, about 12'.
This may not impress you very much. But if you say to him, 'What is
371 times 422?' he will give you the answer to this in just about the
same time, and without needing to write down any figures.
-- W. W. Sawyer, "Mathematician's Delight"