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Wednesday, 21 November, 2001, 19:01 GMT
Test tube holds a trillion computers
DNA diagram
DNA is a natural carrier of information
Ivan Noble

A computer so small that a trillion of its kind fit into a test tube has been developed by researchers at the Weizmann Institute in Israel.

Today it is limited to processing DNA which is synthetically designed. In the future it could process any DNA molecules

Ehud Shapiro
Weizmann Institute
The nanocomputer consists of DNA and DNA-processing enzymes, both dissolved in a liquid.

The inventors believe it could ultimately lead to a device capable of processing DNA inside the human body, finding abnormalities and creating healing drugs.

In the medium term, it could be turned into a tool capable of speeding up the currently labour intensive job of DNA sequencing.

From salesmen to genomes

DNA sequencing is part of the task of cracking the genetic code of interesting organisms as diverse as the pneumonia bug, the tomato and the human body to discover more about the way they function.

Ehud Shapiro and Yaakov Benenson
Professor Shapiro (standing) holds a trillion computers
Professor Ehud Shapiro, head of the Weizmann team, says the DNA computer is an automaton, completing its work without human intervention at each stage of processing.

"Today it is limited to processing DNA which is synthetically designed. In the future it could process any DNA molecules," he told BBC News Online.

The machine's input, output and software program are all DNA molecules.

The Israeli team reads the output of the computer by running the liquid through an electrophoretic gel - the same process that produces the characteristic black and white bands of a DNA fingerprint.

Previous efforts

DNA computing took a leap forwards in 1994 when Leonard Adleman of the University of Southern California used DNA to solve a problem commonly known as the travelling salesman problem.

This problem sets the goal of working out the fastest way of visiting a given set of destinations.

Professor Adleman, co-inventor of the RSA encryption scheme which protects most secure transactions on the internet today, was exploiting the advantages of DNA computing over conventional silicon.

DNA stores a massive amount of data in a small space. Its effective density is roughly 100,000 times greater than modern hard disks. And while a desktop PC concentrates on doing one task at a time very quickly, billions of DNA molecules in a jar will attack the same problem billions of times over.

Professor Shapiro and his team have taken a different approach.

Their goal was not to harness the power of biological computing to solve weighty mathematical problems, but to build a nanoscale computer which takes naturally occurring information-bearing biological molecules such as DNA as an input.

Their success in creating a nanomachine that works on synthetically produced short DNA strands is a huge step towards this goal.

Mathematical inspiration

DNA computing research was inspired by the similarity between the way DNA works and the operation of a theoretical device known as a Turing machine and named after the British mathematician Alan Turing.

"Turing machines process information and store them as a sequence, or list of symbols, which is very naturally related to the way biological machinery works," Professor Shapiro said.

The nanomachine devised by his team is a special case of the Turing machine: a two-state, two-symbol automaton.

It distinguishes between two symbols, like the zeroes and ones of a conventional electronic computer.

The Israeli team's DNA computer is described in more detail in the journal Nature.

See also:

10 Sep 01 | Sci/Tech
Processing power of single cells
03 Sep 01 | Sci/Tech
Visions of a wired future
12 Jan 00 | Sci/Tech
DNA computers take shape
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