Archives - Biology: Page 26
Author: paul carson (Mon Feb 13, 2006 2:59 am)
Title: BIOLOGY - genes
A gene’s instructions can be edited by cellular machinery to convey multiple meanings, allowing a small pool of protein-coding genes to give rise to a much larger variety of proteins.
That such alternatives splicing of genetic messages is possible was long understood. But only when the genome sequences of human and other organisms became available for side-by-side comparison did geneticists see how widespread alternative splicing is in complex organisms and how much the mechanism contributes to differentiating creatures with similar gene sets.
Alternative splicing enables a minimal number of genes to produce and maintain highly complex organisms by orchestrating when, where and what types of proteins they manufacture.
The classical view of gene expression was simple: a DNA gene is first transcribed into RNA form, then cellular splicing machinery edits out “junk” stretches called introns and joins meaningful portions called exons into a final messenger RNA (m RNA) version, which is then translated into a protein. As it turns out, these rules do not always apply. In complex organisms, the initial RNA transcript can be alternatively spliced-exons may be discarded and introns, or portions of them, retained- to produce a variety of mRNA, and thus different proteins, from a single gene.
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