LiveScience.com has published an article regarding the research work done by Joseph Jacobson of the Molecular Machines group at MIT in developing minature robots that mimic the way living cells replicate DNA.
In order for a cell to replicate it’s DNA, enzymes known as polymerases in the nucleus read the structure of the DNA and assemble nucleotides, the basic building block of DNA floating in the nucleoplasm, in the correct order to match the original. In addition to being self-assembling, many DNA polymerases are self-correcting: able to excise incorrect sequences of nucleotides and continue building the chain in the correct order.
Jacobsen has combined the functionality of the external assembler (the DNA polymerase) with the building blocks (the nucleotides) into a tiny robot that comes in two colors: green (G) or yellow (Y) that move by floating on a cushion of air. Each is individually programmed so that it will connect to a green robot on one side and a yellow on the other, forming chains 5 robots long (eg. YGGYY or GYYGG). They also are able to tell if their neighboring robots are incorrect, and if so, disconnect in order to correct the sequence.
The full text of the article is available here.