The first living organism to carry and pass down to future generations an expanded genetic code has been created by American scientists, paving the way for a host of new life forms whose cells carry synthetic DNA that looks nothing like the normal genetic code of natural organisms.
Researchers say the work challenges the dogma that the molecules of life making up DNA are “special”.
Organisms that carry the beefed-up DNA code could be designed to churn out new forms of drugs that otherwise could not be made, they have claimed.
“This has very important implications for our understanding of life,” said Floyd Romesberg, whose team created the organism at the Scripps Research Institute in La Jolla, California. “For so long people have thought that DNA was the way it was because it had to be, that it was somehow the perfect molecule.”
From the moment life gained a foothold on Earth the diversity of organisms has been written in a DNA code of four letters. The latest study moves life beyond G, T, C and A – the molecules or bases that pair up in the DNA helix – and introduces two new letters of life: X and Y.
Romesberg started out with E coli, a bug normally found in soil and carried by people. Into this he inserted a loop of genetic material that carried normal DNA and two synthetic DNA bases. Though known as X and Y for simplicity, the artificial DNA bases have much longer chemical names, which themselves abbreviate to d5SICS and dNaM.
In living organisms, G, T, C and A come together to form two base pairs, G-C and T-A. The extra synthetic DNA forms a third base pair, X-Y, according to the study in Nature. These base pairs are used to make genes, which cells use as templates for making proteins.
Romesberg found that when the modified bacteria divided they passed on the natural DNA as expected. But they also replicated the synthetic code and passed that on to the next generation. That generation of bugs did the same.