[Paleopsych] Introns: the "junk DNA" that controls gene expression

Steve Hovland shovland at mindspring.com
Sun Apr 3 16:45:37 UTC 2005


In the 1960s non-bacterial (eukaryotic) ribosomal RNAs (rRNAs) were found 
to be synthesized as a long precursor RNA which was subsequently processed 
by the removal of apparently functionless internal "spacer" sequences. 
Since bacterial (prokaryotic) rRNAs were more compactly organized, it was 
reasonable to ask whether the first rRNAs to evolve had the spacer 
sequences, which subsequently decreased in prokaryotes, or whether the 
spacer sequences were later acquired in eukaryotes.
In the 1960s a similar processing was found to apply to eukaryotic 
precursor messenger RNAs (pre-mRNAs; Scherrer et al. 1970). In the mid 
1970s it was found that the some of the internal sequences interrupted the 
protein-encoding part of the corresponding mRNAs. The internal sequences 
which were removed were named "introns", and what remained in the processed 
mRNA constituted the "exons". Since the phenomenon had already been 
described for rRNA it should have been no big deal to find that it also 
applied to other RNAs, but many, including the author of these pages, were 
surprised that protein-encoding regions were interrupted. The same 
questions remained.

Google:  http://www.google.com/search?hl=en&q=introns&btnG=Google+Search

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