CRI听力:Scientists build DNA from scratch to alter life's blueprint

Yeast is a tiny ingredient of everyday life.

But now scientists around the world, including here in China, are using it to shape a new frontier of genetic study by creating yeast that operates with custom-made DNA.

A baker carefully adds yeast to his dough before kneading and shaping it into the perfect sized loaf.

Without the yeast, the bread wouldn't rise in the oven - making it a vital ingredient.

That same yeast could soon also help scientists learn how to build redesigned human DNA from scratch.

New York University scientist Jef Boeke has teamed up with an international scientific group, including a team from Tsinghua University in China, to make yeast that works with chunks of man-made DNA.

In other words, they are working to redesign the organism's DNA and create it from scratch.

Boeke believes it's a good stepping stone towards tackling the bigger DNA codes of mammals, including people.

"You can think of the genome of the yeast as a book with many chapters, 16 to be exact, because yeast has 16 chromosomes. And what we are doing is we could just rewrite the exact same book but that wouldn't be very interesting. So what we are doing is essentially coming out with a new edition of the book where we are making a major revision and we are enabling the book to do something it could never do before," Boeke said.

The process to redesign yeast DNA involves using a computer program to edit its natural sequence.

The new edited sequence is then used as a blueprint to build artificial DNA that is inserted into yeast cells for monitoring.

The deleted sequence can be used later on to deliver a different instruction to the cell than it did before.

Leslie Mitchell, a Post-Doctoral Fellow with the Boeke Lab explains:

"Rather than starting with what exists in nature and making changes to see what happens, we can do this bottom up approach where we design whole systems from scratch and see if they work as we predict."

Biologist June Medford is doing similar research with plant DNA and is watching the yeast project closely.

She is genetically engineering plant DNA to be able to detect pollution and explosives.

She says one day, bomb sniffing dogs could be replaced by bomb sniffing plants.

"We've basically encoded a computerized detection technology in the plant. So now if you want to detect something like a bomb in an airport we can make a plant do that. And our sensitivity is about down to that of a dog. So, it's very, very sensitive." Medford said.

While many scientists believe that the success of this project is a step forward to new possibilities, many moral and ethical dilemmas are also concerned as of reconstructing DNA world.

Leslie Mitchell says they are aware of the challenges in the study and believe maintaining an open dialogue is key.

"I think transparency and engaging all the interested parties and stake holders that are involved and that involves talking to ethicists, policy makers, regulators, scientists, the general public. I want my mom to be ok with this. And I think a major component will need to be education," she noted.

The project has so far reported building about one-third of the yeast genome. Boeke hopes the rest of the construction will be done by the end of the year.