Lecture explores life by other means

Lecture explores life by other means

February 23, 2015

February 23, 2015

The lecture, entitled "Where Biochemical Causality and Emergence Meet," was part of a special session: "Searching for Alternative Chemistries of Life on Earth and Throughout the Universe."
 
The interlinked lectures posed fundamental questions regarding the nature of life and plausible alternatives to what biologists refer to as “the central dogma,” which describes the flow of genetic information from DNA to RNA to proteins.
 
The central dogma neatly describes a process underpinning all known life on earth. But could another system lead to alternative life forms on another planet? Could such life forms actually exist on earth, invisible to traditional methods of analysis?
 
Chaput’s lecture outlined his laboratory’s research into an alternative nucleic acid, which could act as a carrier of heritable genetic information, much in the manner of DNA and RNA. Such weird, atypical nucleic acids are known as XNA molecules, where the X stands for an alternate form of sugar, replacing deoxyribose (from DNA) or ribose (from RNA) with something else.
 
One intriguing XNA molecule Chaput described is known as threose nucleic acid (TNA). A TNA molecule uses the same 4-letter genetic alphabet as DNA and RNA and is capable of self-assembling into helical structures, allowing it to base pair not only with itself but with DNA and RNA as well.
 
Chaput outlined a technique known as molecular evolution, which allows researchers to mimic Darwinian evolution in the laboratory. Large libraries of TNA molecules are exposed to successive rounds of selection and amplification in the presence of an arbitrary target molecule.
 
As Chaput described, the process is similar to a colony of microbes exposed to an antibiotic. While most will die, a few will survive, bearing antibiotic resistance. Similarly, a few TNA molecules capable of folding into desired functional forms and binding with biological entities like proteins emerge from repeated rounds of molecular evolution.
 
Chaput offered the tantalizing possibility that TNA (or something like it) may have acted as an evolutionary stepping stone between a long-lost earlier genetic system and the modern regime defining all life on earth currently recognized by biology.

In addition to his appointment at the Biodesign Institute, John Chaput is a 
Professor in ASU's Department of Chemistry and Biochemistry
 

 
Written by: Richard Harth
Science Writer: Biodesign Institute
richard.harth@asu.edu