Final answer:
RNA editing in Trypanosomes, particularly in Trypanosoma brucei, involves the addition and deletion of uracil nucleotides to correct pre-mRNAs for functional protein synthesis. This complex editing process differs from typical mRNA processing in eukaryotes and is an evolutionary remnant from ancient RNA-based cellular mechanisms.
Step-by-step explanation:
In Trypanosomes, RNA editing indeed involves the addition and deletion of uracil nucleotides. This process is particularly important because the pre-mRNAs of Trypanosomes, including Trypanosoma brucei which causes sleeping sickness in humans, do not have the correct sequence to code for functional proteins. The editing process adds the missing U nucleotides needed for a functional mRNA and subsequently the correct protein synthesis.
The mRNA editing in Trypanosoma brucei is different from standard mRNA processing in eukaryotes since it involves significant post-transcriptional modifications which usually don't occur in most other eukaryotes. Such extensive RNA editing in Trypanosomes can be seen as a derived feature that compensates for the 'unfinished' mRNAs transcribed from their mitochondrial DNA.
RNA editing is not unique to Trypanosomes and is observed in some plants and mammals, which suggests an evolutionary holdover from ancient times when RNA molecules were responsible for catalyzing reactions before proteins took over these functions. This process varies depending on cellular conditions, indicating a regulatory aspect of gene expression that can be traced back to the prokaryotic origins of mitochondria.