Newspaper article The Christian Science Monitor

Artificial Yeast Chromosome Brings Science One Step Closer Synthetic Life

Newspaper article The Christian Science Monitor

Artificial Yeast Chromosome Brings Science One Step Closer Synthetic Life

Article excerpt

Saccharomyces cerevisiae, the humble brewer's yeast cell, just got a designer makeover.

By rebuilding yeast chromosome III (which has 316,617 base pairs), a team of researchers has managed to create the very first synthetic eukaryotic chromosome.

Their findings appear in a paper titled "Total Synthesis of a Functional Designer Eukaryotic Chromosome," published in Science on March 27.

Dubbed synIII, this new chromosome is much smaller, with more than 43,000 fewer base pairs than the chromosome III that nature gave it.

Compared with humans, who have 23 pairs of chromosomes, and bacteria, which has just one chromosome, yeast has 16 chromosomes.

Yeast's chromosome III is "a sentimental favorite" among scientists, Jef Boeke, director of NYU Langone Medical Center's Institute for Systems Genetics and an author of the study, told the Monitor. In addition to being one of the smallest of the 16 chromosomes, it contains information that determines how a cell is going to reproduce, sexually or asexually, he says.

To make the new chromosome tighter, researchers made some 500 alterations to eliminate sections considered repetitive or unnecessary for the cell to grow.

First they got rid of so-called junk DNA, such as repetitive base pairs, and jumping genes, which randomly move around and cause mutations, left by viruses that integrated in the yeast DNA and are causing damage.

Next they inserted DNA sequences called loxPsym sites, to enable "genome scrambling," a process that allow scientists to shuffle genes. On their own, loxPsym sites cannot carry out genome scrambling. For that, the cell needs to have Cre - specifically engineered genes from bacterial viruses.

After the artificial chromosome containing the loxPsym sites is ready, Cre is then introduced, permitting recombination.

"Imagine a deck of cards," said Dr. Boeke in a press release. "We can pull together any group of cards, shuffle the order and make millions and millions of different decks, all in one small tube of yeast. Now that we can shuffle the genomic deck, it will allow us to ask, can we make a deck of cards with a better hand for making yeast survive under any of a multitude of conditions, such as tolerating higher alcohol levels?"

Simply put, the scrambling technique can help scientists construct different kinds of yeast cells, where genes can be arranged to make the cells serve different purposes, from producing biofuels to bread. …

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