hnRNAHeterogeneous nuclear RNA (hnRNA) is also called pre-mRNA. It's an incompletely-processed single strand of ribonucleic acid (RNA), and when it's completely processed it becomes mature mRNA.
In nature, hnRNA of eukaryotic cells only exists for a brief time prior to its complete process into mRNA. During its processing, the hnRNA must be spiced to eliminate segments called introns; exons, the other type of segment, code for proteins, but introns are often made up primarily of junk coding and need to be thrown out.
hnRNA is processed by spliceosomes, small organelles in the nucleus that are composed of protein and RNA. After eliminating the introns, other new non-coding segments are attached to the front and back ends (also called the 5' and 3' codons) of the new mRNA. After processing, the mRNA is ready to use by the ribosomes.
The splicing process of hnRNA is of great interest to geneticists; it is undergoing research to determine how it might be usable to change DNA expression in a cell.
Web Resources On hnRNA
Discovery of splicing
Transcription Products
Book Resources On hnRNARNA: Catalysis, Splicing, Evolution by Belfort & Shub
Transcription and Splicing: Frontiers of Molecular Geology by Hames & Glover
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