"Not only can we make designer changes on a computer, but we can make hundreds of changes through a chromosome and we can put that chromosome into yeast and have a yeast that looks, smells and behaves like a regular yeast, but this yeast is endowed with special properties that normal yeasts don't have."
The synthetic yeast chromosome was based on chromosome number 3, but scientists deleted large parts of it that were considered redundant and introduced further subtle changes to its sequence - yet the chromosome still functioned normally and replicated itself in living yeast cells, they said. "We took tiny snippets of synthetic DNA and fused them together in a complex series of steps to build an essentially computer-designed chromosome 3, one of the 16 chromosomes of yeast. We call it synIII because it's a completely synthetic derivative that has been engineered in a variety of interesting ways to make it different from the normal chromosome," Boeke said.
The achievement was compared to climbing Mt Everest in its labour-intensive complexity, as it involved stitching together 273,871 individual building blocks of DNA - the nucleotide bases of the yeast's genes - in the right order, and removing about 50,000 repeating sequences of the chromosome that were considered redundant.
"When you change the genome you're gambling. One wrong change can kill the cell. We have made over 50,000 changes to the DNA code in the chromosome and our yeast still lived.
"That is remarkable, it shows that our synthetic chromosome is hardy, and it endows the yeast with new properties," Boeke said.
- Independent
