Oops! I thought I was being careful to only say 'reverse translation'
but obviously I wasn't... Thanks for looking over my shoulder.
> Information loss for eucaryotic cells (for all I know about it) seems
> to not occur until the mRNA is generated. At this point the introns
> are removed and the 5' and 3' regions which govern the RNA polymerase
> action are cut off. How you could possibly reconstruct them is not known
> to me. I would say the lesser information loss occurs at mRNA
> translation to protein. You could, in theory, duplicate the codons since
> you have a limited number of selections. How you would replace the
> control regions and introns is harder. Codon usage is specific for
> individual creatures and the wrong codon choice could doom your coded
> protein in certain instances. I work on Entamoeba histolytica and it
> has never yet been seen to use 4 codons and another 6 are quite rare.
> E. histolytica is a very AT rich organsim. Certain thermophilic organisms
> are very GC rich.
Now you're going a bit fast. What are the 5' and 3' regions?
And I'm not following the possible reconstructability of the codons
from mRNA to protein. Has the 61 letters ---> 20 amino acid thing
been broken by this time? (Maybe that's what the 5' and 3' regions
have to do with?) The AT-rich vs. GC-richness is interesting. Does
anyone know why that is the case?
> > if reverse transcription is accompanied by a random process which selects
> > codons within the space of possible sequences to code for a protein, then
> > all the information in the original DNA sequence can appear in the
> > reverse translated one.)
>
> As I mentioned above, in certain instances, certain codon choices might
> spell doom if you ever wanted a functional protein to be made again. They
> aren't sure why this is, as far as I know (not far) but too many Gs and Cs
> in Entamoeba are thought to gum up the RNA polymerase machinery if they
> occur in certain spots, so the RNA strand prior to mRNA doesn't get made.
> Certain codons in certain organisms might also harm the ability of the
> mRNA to be made from the splicing machinery. And lots of As and Ts in
> thermophilic organisms would result in the DNA being denatured (AT-rich
> regions melt more readily than GC rich regions since ATs are held together
> by two hydrogen bonds while GC pairs have three) at the temperatures at
> which they exist.
Fascinating. So there are 'higher-level' constraints on relative
abundances on the bases?
-Greg