Resurrecting Genomes

View Images

In tomorrow’s New York Times, I have an article about how to reconstruct a genome that’s been gone for 80 million years. The genome in question belongs to the common ancestor of humans and many other mammals (fancy name: Boreoeutheria). In a paper in this month’s Genome Research, scientists compared the same chunk of DNA in 19 species of mammals. (The chunk is 1.1 million base pairs long and includes ten genes and a lot of junk.) The researchers could work their way backwards to the ancestral genetic chunk, and then showed they could be 98.5% certain of the accuracy of the reconstruction.

There are some pretty astonishing implications of this work. For one thing, it should be possible to synthesize this chunk of DNA and put it in a lab animal to see how it worked in our ancestor. For another, the scientists are now confident that they will be able to use the same technique to reconstruct the entire genome in the next few years, if the sequencing of mammal genomes continues apace. Could scientists some day clone a primordial Boreoeutherian? It’s not impossible.

On the down side, this method will not work for just any group of animals you want to pick. Mammal evolution was rather peculiar 80 million years ago: a lot of branches sprouted off in different directions in a geologically short period of time. That makes the 19 species the scientists studied like 19 different fuzzy images of the same picture. Other groups of species had a very different evolutionary history, and one that may make genome reconstruction impossible. If you yearn for the day when Jurassic Park becomes real, you will have to conect yourself with a swarm of shrew-like critters. If they did somehow manage to break out of a lab, I suspect they would get eaten by the first cat to cross their path.