Artificial chromosome created

In a major step forward in biological engineering, researchers have created the first 'designer' artificial yeast chromosome, publishing their landmark work in the journal Science. Brewer's yeast, Saccharomyces cerevisiae, has 16 chromosomes and shares 2,000 genes with humans. Previously researchers lead by Craig Venter have created synthetic chromosomes for bacteria, but yeast is a more complex organism with bigger chromosomes contained within a nucleus, similar to human cells.

Led by Dr Jef Boeke at New York University, the researchers made a synthetic version of yeast chromosome III, named SynIII, by designing and building nearly 275,000 base pairs of DNA - tens of thousands fewer than the number in the original chromosome. They cut the size down by removing repeated sections in the original DNA and some of the DNA that doesn't encode instructions for making proteins. Despite having more than 50,000 changes to its DNA code, the designer yeast were still able to grow and multiply as usual. It also gained new functions, such as the ability to scramble the new chromosome on cue to make future genetic manipulations easier.

The new designer chromosome is the first step in an international project aiming to build yeast's entire genome over the next few years. Scientists are also developing synthetic genes that would transform yeast into biological factories, for example producing antibiotics and turning agricultural waste into biofuel.

The researchers also think that it might one day be feasible to synthesise entire plant and animal chromosomes, or even whole genomes. That may be a long way off, but certainly mini chromosomes containing tens or even hundreds of genes are definitely within the foreseeable future, according to the team.