Scientists Create Synthetic Yeast Chromosome

For the first time, scientists have engineered a functional, intact eukaryotic chromosome in a strain of yeast. This is an important step in the field of synthetic biology, which aims to eventually design new microorganisms that will produce medicines, biofuels and raw materials for fuel.

Over the past few years, several types of bacterial chromosome and viral DNA have been synthesised. However, eukaryotes like yeast (and humans) have not previously had their chromosomes (thread-like lengths of DNA and accessory proteins) created artificially by scientists in the lab.

In a paper published in the journal Science, the team of international scientists describe how their seven-year effort to construct the chromosome (named synIII) was finally accomplished, and how the chromosome was then successfully inserted into brewer’s yeast.

SynIII contains 273,871 DNA base pairs, fewer than the 316,667 in native yeast. This disparity can be explained by the many alterations made by the researchers to the chromosome (removing bases unnecessary for reproduction and growth and adding new base pairs to tag DNA as synthetic or natural). The fact that the chromosome was functional despite these changes was a source of great amazement for the researchers; Dr Boeke, the leader of the study, remarked that “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 live”.

Survival was achieved by ‘shufflling’ the genes of the yeast around, allowing them to manipulate the DNA without damaging the chromosome. The shuffling technique could aid the development of yeast strains that could make rare medicine (e.g. artemisin for malaria) or more efficient biofuels. The next challenge will be synthesising larger yeast chromosomes (chromosome III was synthesised in this study because it is one of the smallest) at minimum expense.

To view the original article, please visit: http://www.sciencemag.org/content/early/2014/03/26/science.1249252