An anonymous reader quotes a report from The Guardian: Scientists have created the world’s first living organism that has a fully synthetic and radically altered DNA code. In a two-year effort, researchers at the laboratory of molecular biology, at Cambridge University, read and redesigned the DNA of the bacterium Escherichia coli (E coli), before creating cells with a synthetic version of the altered genome. The artificial genome holds 4m base pairs, the units of the genetic code spelled out by the letters G, A, T and C. Printed in full on A4 sheets, it runs to 970 pages, making the genome the largest by far that scientists have ever built. The DNA coiled up inside a cell holds the instructions it needs to function. When the cell needs more protein to grow, for example, it reads the DNA that encodes the right protein. The DNA letters are read in trios called codons, such as TCG and TCA.
The Cambridge team set out to redesign the E coli genome by removing some of its superfluous codons. Working on a computer, the scientists went through the bug’s DNA. Whenever they came across TCG, a codon that makes an amino acid called serine, they rewrote it as AGC, which does the same job. They replaced two more codons in a similar way. More than 18,000 edits later, the scientists had removed every occurrence of the three codons from the bug’s genome. The redesigned genetic code was then chemically synthesized and, piece by piece, added to E coli where it replaced the organism’s natural genome. The result, reported in Nature, is a microbe with a completely synthetic and radically altered DNA code. Known as Syn61, the bug is a little longer than normal, and grows more slowly, but survives nonetheless.