Jurassic mammels...

[johnny861]

Extinct Creature's Genome Reconstructed
Technique uses computers and DNA comparison to travel back in time

Reminiscent of the movie Jurassic Park, researchers have reconstructed part of an ancient mammal's genome using a technique that allows the resurrection of DNA without the need for fossils.

Instead, they used computers and existing mammalian genomes to rebuild with 98% accuracy part of the genome of the common ancestor of all placental mammals, including humans. The creature was a small shrew-like animal that lived in the forests of Asia more than 80 million years ago.

By comparing DNA sequences from humans and 18 other species of existing mammals, the researchers built a large segment of the creature's DNA.

The work proves that it's possible to recreate ancient genomes using computers and comparative genomics—the comparison of genomes from different species.

It will allow scientists to understand the evolution of humans and other mammals at the molecular level and—while it would be difficult and expensive—could theoretically allow extinct creatures to be resurrected.

"We will be able to trace the molecular evolution of our genome over the past 75 million years," says project leader David Haussler of the University of California, Santa Cruz. "It's a very exciting new way to think about our origins, a kind of DNA-based archaeology to understand how we came to be."

Better comparison


While Jurassic Park made it seem plausible, extracting DNA from fossils hasn't worked out so well because DNA breaks down over time and, according to Haussler, DNA sequences are typically too fragmented to be useful after about 50,000 years.

Having the DNA of ancient creatures is still desirable, however—although constructing a theme park of extinct animals is low on scientists' list of priorities.

By comparing the human genome to the genome of the ancestor of all placental mammals, scientists could learn more than they can from comparisons with other living species such as mice and chimpanzees, says Haussler.

Such a comparison would reveal how DNA sequences change in lineages leading to different species, yielding insight into the evolution of certain characteristics such as fluent speech in humans.

"If we find a DNA sequence in the human genome that is missing in the corresponding place in the mouse genome, we can't tell whether that DNA was inserted in the evolution of humans from the mammalian ancestor or deleted in the evolution of mice," says Haussler. "If the ancestral genome is available, this ambiguity disappears."

Working backwards

Haussler and colleagues were able to work backwards because all placental mammals alive today are descended from an ancestor that lived millions of years before the end of the dinosaurs. They have all therefore inherited DNA from that ancestor, and comparing their genomes allows the reconstruction of the ancestor's genome.

Using existing genome comparison software and new algorithms created for the project, the researchers computed genome sequences from different mammals.

They focused on a region called the CFTR locus that includes the gene involved in cystic fibrosis. This region, which comprises one million base pairs of genetic code, has been sequenced for many mammals.

The software looked for alterations, insertions and deletions in the genetic code of mammals that included species of pig, horse, cat, dog, bat, mouse, rabbit, gorilla, chimpanzee and human.

The information was incorporated into a program that simulated the evolution of DNA for the mammalian lineages. By running multiple simulations, the researchers could test the accuracy of their DNA reconstruction.

Comparisons using DNA from species not used in the reconstruction itself confirmed the accuracy of their work.

Haussler hopes the findings encourage more sequencing needed for a complete reconstruction of the ancestral mammalian genome.

"It sounds implausible," says Haussler. "But there's enough information to reconstruct the ancestral genome on the basis of mammals that live today. We just need to sequence the genomes of these living mammals."

The work is reported in the journal Genome Research.

[MysteryMeat]

I got dibbs on the first giant sloth!

[johnny861]

Originally Posted by MysteryMeat

I got dibbs on the first giant sloth!

Hell yea! I'd slap that thing on a radio flyer and take it places with me hehehe

[Taki]

I think we all evolved from Birds in one way or another.