Geneticists have made a huge advance towards the creation of designer artificial organisms by synthesizing the first entire chromosome for yeast. This landmark study was published March 27,2014 in the prestigious journal Science. The ability to design and synthesize chromosomes for artificial life have the potential to alter the world’s energy economy and create innovative cures in medicine.
Chromosomes consist of tightly bound-up DNA and protein. The condensed and coiled configuration of the DNA helps to contain all of an organism’s genetic material within the nucleoid region of bacteria cells or the nucleus of eukaryotic cells (such as humans and yeasts). The tightness of this coiling also plays an important role in determining which of the contained genes get expressed. The synthesis of an artificial chromosome is an important intermediate step between creating an artificial gene and an artificial genome. A single chromosome may have thousands of genes on it. However in non-bacteria life-forms it takes multiple chromosomes to make up a genome. Human cells have 23 pairs of chromosomes. By contrast, yeast cells have only 16.
In 2010 an international team of geneticists created a synthetic bacteria cell, including all of its genetic information. However bacteria have only one chromosome, and that chromosome is quite different from the chromosomes found in eukaryotic organisms such as humans and yeasts. The difference in structure of the chromosome means that bacterial cells have profoundly different mechanisms for how their genes are expressed.
However on March 27, 2014 researchers from the group referred to as “Sc2.0” announced that they had further advanced the field of designing artificial life by synthesizing the first eukaryotic chromosome. This was done using the brewer’s yeast Saccharomyces cerevisiae. To achieve this feat, more than 100 student participants from the “Build-a-Genome” project combined small pieces of genetic information into one long chromosome. Along the way useless, non-coding parts of the chromosome (a.k.a. “junk DNA”) were omitted, and special markers for identification and controlled reorganization were inserted. The resulting chromosome was called “SynIII” and was over 43,000 base pairs slimmer than its wild-yeast equivalent and boasted 500 genetic alterations.
SynIII is only one chromosome out of the 16 found in yeast. However, with this first chromosome completely synthesized, researchers are highly motivated to replicate their achievment with the remaining 15. Because the methods used to synthesize SynIII were so successful, researchers predict that creating yeast cells with exclusively artificial chromosomes can be accomplished within several years. In addition scientists are also toying with the idea of creating entirely new chromosomes as “add-ons” that could be used to generate designer organisms for human use.
The synthesis of artificial chromosomes and the design of living organisms have a seemingly limitless number of potential applications. Because human genes could be fabricated into the chromosomes of artificial yeasts, it would be possible to create disease screenings and drug components using these specially designed organisms as living factories. Already studies are under way to apply such technology towards creating an anti-malaria drug. In addition, artificial yeasts also could be used to generate biofuels to reduce the world’s dependency on oil.
By Sarah Takushi