Genetic Family Tree of All Life Is Bearing Fruit

John Roach
for National Geographic News
September 6, 2006
New cures, supercrops, and secrets of evolution may emerge from the fast-growing branches of the "Tree of Life," scientists say.

The increasing availability of genetic information—and the computer technology to analyze it—is allowing researchers to begin drawing a detailed picture of how life on Earth originated, adapted, and diversified.

"A huge amount of progress has been made over the last decade," said Michael Donoghue, a biologist at Yale University in New Haven, Connecticut.

Donoghue attributes the progress to revolutions in molecular biology and computer technology that allow scientists to see at the genetic level how species are related to each other.

When plotted on a page the information looks like a giant, bushy tree, hence the project's nickname.

Donoghue is part of an army of scientists working in teams around the U.S. to assemble the tree.

Tree Assembly

According to Donoghue, scientists extract information from the Tree of Life by making comparisons among species' genomes.

A genome is an life-form's complete set of DNA. The human genome, for example, contains some 3 billion base pairs, which code for the approximately 30,000 genes that define a person's unique traits. (See a quick overview of human genetics.)

Tree of Life scientists can determine the uniqueness of a particular gene in the human genome by comparing the human genome to genomes of other species.

For instance, they might ask if a particular human gene is shared with chimpanzees, our closest animal relatives. If not, the gene is probably unique to humans. (Related: "Chimps Belong on Human Branch of Family Tree, Study Says" [May 2003].)

If the gene is shared with chimpanzees, is it also shared with some of humanity's more distant relatives, say mice or frogs? What about yeast?

Answers to such questions allow scientists to trace genetic evolution and better understand how genes function. And as more and more species are identified and placed on the tree, these comparisons become more effective and efficient, Donoghue says.

To date, scientists have identified about 1.7 million species living on Earth and estimate that at least 10 million more species await discovery. Millions more species are thought to have gone extinct.

"In trying to figure out how species are related to one another, it immediately becomes clear this is a very large problem that doesn't have an end in sight any time very soon," Donoghue said.

"We're still discovering species, much less figuring out who is related to whom."

The magnitude of the task, Donoghue said, is "enormous."

To help accomplish the task, the National Science Foundation (NSF) established the Assembling the Tree of Life (AToL) project in 2002.

(This news story and the related Pulse of the Planet radio program are funded in part by the National Science Foundation.)

James Collins is NSF's assistant director for biological sciences. He oversees how AToL funding is awarded.

Collins says that fostering collaboration among individual scientists is key to the project's success.

"That's a significant departure from the norm," he said. But the task of assembling the [branches] in today's world requires a new approach to science, he says.

"As you get [the DNA of] more and more organisms sequenced and more and more information about the evolutionary history of particular groups of organisms, it's not a trivial matter to finally come up with the [branches] themselves," he said.

Collins hopes the AToL initiative will eventually establish the major branches on the Tree of Life—giving scientists a clear picture of gene-level differences among mollusks and worms, invertebrates and vertebrates, plants and animals, and so on.

"We can develop a relatively good picture of what the trunk and branches look like before we have—to continue the analogy—all of the leaves done on the tree," he said.

Using the Tree

With the trunk and branches firmly established, Collins says, scientists will be able to use the Tree of Life as a research tool and even to fill in missing leaves.

"Based on the knowledge of the organisms that we already have in place, we can make predictions about organisms we don't know a lot about," he said.

For example, Collins says, if scientists want to find an organism that has properties useful in the cleanup of oil spills, they would first turn to microbes that have known beneficial properties and then examine the microbes' nearest relatives for good matches.

To help engineer new crops, agricultural researchers might study genetic traits that make crops drought resistant.

Donoghue, the Yale biologist, says scientists can use the tree to understand where emerging infectious diseases originate and to search for organisms that have evolved resistance to the diseases in question. Such clues can lead to the development of new drugs, he says.

"Applications are everywhere," he said.

So too are discoveries, he adds. For example, Tree of Life researchers have learned that fungi—mushrooms and the like—are more closely related to animals than plants.

"This is not just dotting I's and crossing t's," Donoghue said—assembling the tree is more than simply organizing previously known information.

"There are some really exciting things being discovered."

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