DNA

From PhiloWiki

How did DNA evolve naturally?

DNA evolved naturally

Most scientists agree life as we know it cannot exist without DNA as the storehouse of genetic code, RNA as the genetic messenger, and proteins to carry out the chemistry of reproduction. Can any one of these three key molecules have existed as the precursor of the other two, serving as both chicken and egg?

Evidence is mounting that "it was an RNA World at the dawn of life as the Earth began to cool," said Breaker, who added that he and his colleagues can create dual-purpose genetic enzymes in the laboratory out of either RNA or DNA. "These genetic enzymes have the chemical sophistication, the full catalytic ability, to do many of the fundamental reactions we see in biology today. I am confident one will be created soon that can replicate itself."

He added that the new DNA enzyme he crafted destroys RNA with impressive efficiency at a rate 10 million times faster than it would decay naturally, although the protein the enzyme mimics acts much faster still.

No naturally occurring DNA enzymes have been found to date, but such a discovery would not surprise Breaker. The discovery nearly two decades ago of naturally occurring RNA enzymes, or ribozymes, earned Yale biochemist Sidney Altman and University of Colorado researcher Thomas Cech the 1989 Nobel Prize in Chemistry. In separate experiments, Altman and Cech exploded the myth that RNA is merely a passive carrier of genetic code incapable of triggering cell activity.

Referring to the dozen or more DNA and RNA enzymes created in his laboratory in recent months, Breaker said, "We believe these are like ancient molecular 'fossils' that might have been found stomping around the planet -- or more likely floating in the seas -- during the Archean Era between 3.8 and 4 billion years ago."

While the Yale biologists created the versatile protein mimic from DNA, Breaker theorizes that a similar enzyme could be created with RNA, which many scientists believe is the strongest candidate for being the precursor of all other life forms. In addition to RNA's dual function as genetic molecule and as enzyme, RNA serves important roles in all living systems as the carrier of genetic instructions from DNA and as the orchestrator of all protein synthesis.

"This is exactly what you would expect if RNA invented these processes during the 'RNA World,'" Breaker said. "Because DNA is about a million times more stable than RNA, DNA most likely evolved later as a safe storehouse for the genetic code first found in RNA. Similarly, proteins probably evolved that were more efficient chemical catalysts, eventually driving most RNA enzymes extinct and relegating RNA to a more limited role."

The discovery that nucleic acids can raid the tool box of proteins means "the RNA World could have been a very sophisticated place," Breaker said. "The earliest RNA could have had access to all of these chemical helpers now used by proteins. Instead of working from a very primitive palette, varieties of RNA could have evolved that had a very rich chemical capability early on.

Molecular "Fossils" of Early Life from Yale University, exoScience

DNA could not have evolved naturally

The earth is about 4.5 billion years old. Fossils extend back 3.5 billion years. Long before you get to the “straightforward rise of the eye,” you assume the straightforward formation of prebiotic compounds (in a violently hostile young Earth), the straightforward assembly of the first self-replicating molecules, the straightforward emergence of RNA molecules, the straightforward transition from an RNA world to the DNA-protein world, the straightforward emergence of starter proteins, the straightforward emergence of gene duplication and divergence, the straightforward assembly of a workable membrane to protect and feed the RNA, DNA, and/or protein molecules, and the straightforward positioning of all the molecular components in the correct locations with respect to on another.

How did DNA get created so quickly?

• The Case for a Creator - Lee Strobel. The book is full of recent scientific research/evidence from cosmology, physics, biochemistry, and biology (including DNA and genetics).

• “Mere Creation” by William Dembski (1998), which includes a chapter on DNA formation and the origin of information.