Every living organism on this planet, from single-celled bacteria to humans, has a genome. You can picture the genome as the ultimate instruction manual, holding all the information an organism needs to survive and function. These instructions are stored on long DNA sequences called chromosomes. The synthetic genome created by the Venter group was based on one of these circular strands of DNA from a bacterial called Mycoplasma genitalium, whose DNA had already been sequenced. This meant that scientists knew exactly what the string of DNA (made of four letters A, T, G, and C) in the bacteria's chromosome looked like, and likely had it written in a computer file as a long string of As, Ts, Gs, and Cs.
Did You Know?
Multicellular organisms like humans and other animals, typically have genomes made up of several long strands of DNA (called chromosomes). Bacterial genomes, however, typically only have one circular chromosome encoding everything the cell needs.
The Venter group took this file, representing the DNA sequence of Mycoplasma genitalium,and divided it into 101 separate pieces. These pieces were sent to various labs, where machines were used to chemically synthesize DNA molecules corresponding to the letters in the files. These 101 DNA molecules were than pieced back together like a jig-saw puzzle, using various methods, to form the complete Mycoplasma genitalium genome. But wait a minute, you might say, what's the big deal here? After all, they didn't make a genome from scratch; they've only pieced back together a genome we already know about. Well, there are a couple of big deals here actually. First, synthesizing and piecing together pieces of DNA is not an easy process. The previous record for the largest synthesized DNA was about 32, 000 nucleotides long, while the synthesized Mycoplasma genitalium genome has almost 600, 000 nucleotides. But most importantly, this project has shown that it is possible to stitch together pieces of DNA to form the genome of a functional organism.
Did You Know?
The human genome has over 3 billion nucleotides!
In the future, it may be possible to introduce genes and other changes to these pieces prior to stitching them together. In this way, scientists of the future may be able to create simple organisms which can digest harmful toxins, clean up oil spills, or even produce energy to fuel our cars and homes. The possibilities are limited only by our imaginations. But there are still many hurdles between this recent discovery and a future where custom-made organisms are commonplace. Some of these hurdles are technical: scientists still have to find a way to transplant the synthetic genome into living cells. But the most difficult hurdles might have little to do with science and everything to do with ethics and morality. Just as we can use synthetic organisms to save the world, if we're not careful, we can also use these organisms for bio-warfare with disastrous consequences. The Venter group may have ushered in a new age of biology, where biologists are creators rather than simple observers, but what we make of these new powers will be even more important than the discovery itself.
Article first published June 23, 2008
The J. Craig Venter Institute
How to sequence a genome
Wired article about bacteria and oil spills
David is a PhD candidate in the Department of Medical Genetics at the University of Toronto. He graduated from UBC with a Bachelor's in Biochemistry and Computer Science. During his spare time, David helps out with local science outreach programs like Let's Talk Science.