Tony Smith: RCA has advantages over PCR

PCR was invented by Californian scientist Kary Mullis, and won him a share of the Nobel Prize for Chemistry in 1993.

PCR will target and duplicate a specific stretch of DNA, producing millions of copies in just a few hours. It works by exploiting processes that occur naturally in living cells, using an enzyme to copy a DNA template over and over again.

The amplification process makes it much easier for researchers to study the genetic code and has made PCR a standard technique for scientists investigating the human genome. It is used in the mapping of genes, can help diagnose disease and is a crucial tool in the "fingerprinting" techniques used to track down criminals.

Micro-organisms

An alternative technology, called Rolling Circle Amplification (RCA), was discovered in 1995 by Paul Lizardi at Yale University School of Medicine. It borrows some of the same molecular "machinery" used by viruses to rapidly churn out copies of their DNA in infected cells.

In RCA, the enzyme reads around a circle of DNA - literally "rolling out" long, repeated sequences of DNA.

Amersham Pharmacia Biotech has joined forces with Molecular Staging Inc, to bring the Yale technology to the marketplace. They believe RCA has a number of advantages that will help it challenge the older technology's pre-eminence in the laboratory.

Tony Smith, Vice President for Research and Development in UK for AP Biotech, says RCA does not require the processing temperature to be changed up and down as is required with PCR.

"Ten-billion-fold amplification can be achieved in as little as one to two hours. It can give you that without having to cycle the temperature and can allow you to get very good quantitation."

He also believes RCA is much more effective in amplifying much larger stretches of DNA, including gene-sized fragments.