Jurassic Molecules

Dateline: 06/18/98

Scientists announced last week the successful reproduction of a possible precursor to all life on Earth. The molecules consist of a part of DNA and the molecular "scissors" responsible for destroying messenger RNA in humans.

Using a technique called test tube evolution, scientists created a nucleic acid enzyme, the first known enzyme that uses an amino acid to start chemical activity. Scientists hope that the creation of this molecule will lead to the elusive precursor. The precursor, by definition, will have to contain both the genetic code for replication and an enzyme to trigger self replication.

At this point, no naturally occurring hybrid enzymes have been found. Scientists speculate that such enzymes may exist in nature and most certainly existed in Earth's early history.

Scientists have known for some time that the key ingredients for life are DNA, RNA, and proteins. An interesting chicken-egg dilemma has developed: which came first, RNA, DNA, or proteins? Many believe that a replicating RNA molecule is the likely precursor to all life on Earth.

RNA serves as both a genetic molecule and an enzyme in the body, which scientists believe strongly suggests the likelihood of an RNA precursor to all life. They speculate that RNA was first, followed by DNA, the much more stable of the two. It would serve as an efficient storehouse for the genetic code. Proteins, better catalysts than RNA, likely evolved later as well. At some point, the current three-based system developed from the initial one-based system of RNA.

Scientists hope that these scissors molecules may also have practical uses in medicine, since the molecules can efficiently shred specific DNA. Theoretically, it may be possible to tailor such a molecule to attack and shred harmful DNA from pathogenic organisms. These molecules could be made to be activated only in specific circumstances.

What do you think? Have we found a possible precursor to life? What are the important assumptions that are being made about the natural processes on Earth? We've received much mail in the past about the validity of such studies. Come over to the Biology Forum and share your thoughts, opinions, and feelings.

For additional information see:

• Molecular "Fossils" Of Early Life
  News release about the study from EurekAlert.