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Released December 2, 2003

By Christopher Mapp

HATTIESBURG - Fifty years after legendary scientists James Watson and Francis Crick discovered the structure of DNA, researchers are still unlocking its mysteries.

And a new model of the DNA molecule, designed by a biology professor at The University of Southern Mississippi, is helping students join in that discovery.

To aid in the understanding of genetic coding, Dr. Ray Scheetz has developed a highly durable plastic DNA model that allows students to handle interchangeable blocks, fitting them together to form the molecule's familiar helix shape. This interaction, Scheetz said, makes a lasting impression on students because of its strong visual component.

"Kids learn in high school that genetic code is contained in the order of these things called bases," Scheetz said, grasping a colored block from the model. "They come in four flavors - A, T, C and G. Most of us just memorize this, but I wanted a model that was intuitive, something students can snap together and say, 'Ah, that's how that works!'"

The carrier of genetic code and the key molecule of heredity, DNA (deoxyribonucleic acid) is twisted into packets and tucked into the nucleus of every living cell. Its structure was discovered by British scientists Watson and Crick in 1953, and since their discovery, DNA research has grown exponentially.

Scheetz said that ever since molecular biologists have learned to manipulate the sequences of DNA, they have attained the ability to "do some pretty amazing things." Among the wonders is gene therapy.

"Scientists can now cut the sequence out of DNA molecules and paste them on another, like a word processor. That means the future of medicine is going to see a lot of gene therapy, where you correct the defects instead of taking expensive medicines.

"It is very possible that it will get to the point where they can fix defective sequences in DNA or even repair them," Scheetz said.

Developed over the last three years, Scheetz' instructional model has been tested in freshmen biology labs at Southern Miss this semester, where it has drawn a positive response from students.

Chaquita Washington, 18, a freshman biology major from Natchez, said she liked the way the model allowed her to "see how DNA works."

"You read about the structure and the sequences in the books, but something like this helps it all make sense," Washington said.

Frustrated with less durable models made from cheap materials, Scheetz set out to design his model from quality components. So, he turned to the university's polymer science department for help. Working from 3-D computer drawings of the model, researchers used a "rapid prototyping machine" to make a metal mold overnight - the same kind that would have taken six months to make using traditional methods.

"I've taught courses a long time and I'm familiar with the other models on the market. Some of them look like Tinker toys, with beads representing the atoms. If you're a chemist you can recognize this, but if you're a student, you can't make heads or tails of them," Scheetz said.

The model, made at Excel Plastics in Hattiesburg, will be marketed to high schools and other institutions this year. Southern Miss holds the patent to the model and proceeds from it will go back into the biology department.

"DNA is the blueprint for making all the proteins that make up who you are," Scheetz said. "They make things happen in cells, and make pigments, or why you have brown hair or blue eyes. All the genetic traits break down to protein activity, and DNA has the blueprint for that encoded in its order.

"It's a complicated molecule. But maybe this model, by allowing students to handle it and figure out how it is all interconnected, can help them better understand these building blocks of life."


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April 20, 2004 4:09 PM