The discovery of DNA and RNA was to describe the anatomy of the mechanism whereby heritable information was transferred from generation to generation.
Now the physiology and biochemistry of the mechanism is being described.
Ericka Check in Nature 2007, Hitting the on switch , 448, pp 855-868 discusses RNA interference. This is the process whereby small pieces of RNA regulates the expression of genes. RNA has been seen as the carrier pigeon of the system, that DNA is all. RNA however is important in controlling the transfer of information held by DNA.
Small strands of RNA stick together in pairs and can turn off specific genes. Short interfering RNAs ( siRNAs ) ( also known as short hair pin RNAs ( shRNAs). These act by using a protein (RISC) to cut up the longer messenger RNAs. The small RNAs are able to target messenger RNA through their sequence matches and destroy the messenger RNA. There are also more than 500 miRNA which are directly encoded by DNA.
Methylation has been seen as a prime silencer of gene activity.
It is also possible that the interference pathway may activate genes. if this is the case then a whole new approach to molecular Biology is waiting to be discovered.

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Martin Eastwood

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