Scientists have created the world's first living organism that has a completely synthetic and radically altered DNA code.
The lab-made microbe, a strain of bacteria normally found in the soil and the human intestine is similar to its natural cousins, but survives on a smaller set of genetic instructions.
The existence of the bug shows that life can exist with a limited genetic code and paves the way for organisms whose biological machines are commandeered to make drugs and useful materials or to add new functions such as virus resistance.
In a two-year effort, researchers at the molecular biology laboratory at Cambridge University, and redefined the DNA of the bacterium read Escherichia coli ([coli) before creating cells with a synthetic version of the altered genome.
The artificial genome contains 4m base pairs, the units in the genetic code spelled out with the letters G, A, T, and C. Printed in its entirety on the A4 sheet, it goes to 970 pages, making the genome the greatest superior to a scientist ever built.
"It was completely unclear whether it was possible to make one through so large and if it was possible to change it so much," says Jason Chin, an expert on synthetic biology who led the project. The DNA coil in a cell holds the instructions it needs to work. For example, when the cell needs more protein to grow, it reads DNA that encodes the right protein. The DNA letters are read in triads called codons, such as TCG and TCA.
Almost all life, from jellyfish to humans, uses 64 codons. But many of them do the same job. In total, 61 codons produce 20 natural amino acids, which can be joined together as beads on a string to build some protein in nature. Three new codons are in fact stop signs: they tell the cell when the protein is made, as the complete stop marks the end of this sentence.