This new discovery goes a long way toward explaining why there is so little difference in the DNA make up of species that are so vastly different in
function and appearance. According to this, the real differences don't show up until DNA is used by the cell to create RNA.
MIT biologists have found that alternative splicing of messenger RNA accounts for much of the differences seen between species.
When genes were first discovered, the canonical view was that each gene encodes a unique protein. However, biologists later found that segments of
genes can be combined in different ways, giving rise to many different proteins.
This phenomenon, known as alternative RNA splicing, often alters the outputs of signaling networks in different tissues and may contribute
disproportionately to differences between species, according to a new study from MIT biologists.
This process allows cells to create a much wider variety of proteins than would be possible if each gene encoded only one protein.
Some proteins, including Dscam in fruit flies and neurexin in humans, have thousands of alternate forms. These variant proteins can have vastly
different functions, Burge says.
For example, the full version of a protein may bind to DNA at one end and activate DNA transcription at the other end. If an alternatively spliced
form is missing the activation section, it will compete for binding to the same DNA regions as the full-length protein, preventing activation of
edit on 22-12-2012 by happykat39 because: added quoted material