This is Professor Richard Carthew from
Northwestern University in Evanston, Illinois United States.
And today I'm going to be talking about RNA Interference or
RNAi and its functions and mechanisms in animals.
To understand why RNA Interference or RNAi exists,
it's worth revisiting two classic books from the 19th century.
One that you are no doubt familiar with and one that you may not be so familiar with.
Darwin's Theory of Evolution assumed that features central to survival could be inherited.
Of course, we now know these are our genes.
August Weismann proposed a different theory, though equally revolutionary.
An organism is composed of germ cells that pass
all genetic determinants unaltered to the next generation.
The rest of the body's cells merely accommodate the germ cells.
Or as Samuel Butler said it,
"A hen is only an eggs way of making another egg".
50 years ago, Richard Dawkins modified this theory to state that
the reproductive successive genes should be equal to the organism itself.
All genes should copy together in lockstep with the organism.
If a gene's reproduction is faster than that of the organism,
then it would out compete other genes that reproduce with the organism.
Are there such cheating genes?
The answer is yes.
There are cheating genes that reproduce by
horizontal transmission such as viruses infecting different individuals,
and there are genes that reproduce by
vertical transmission through the germline and creation of new organisms.
These are called transposable elements.
They are integrated into the genome and they reproduce faster than the organism by
replication and insertion of new copies into new sites within the genome.