Scientists Announce an Artificial Chemical System Capable of Darwinian Evolution
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Scientists from the Foundation for Applied Molecular Evolution (FfAME) and the Westheimer Institute for Science and Technology in Gainesville Florida have announced previously that they have taken the next steps towards a synthetic biology.
Presenting their work at the annual meeting of the American Association for the Advancement of Science in Chicago, Dr. Steven Benner described the first example of artificial genetic system was capable of supporting Darwinian evolution.
The presentation occurred at a session covering "Weird Life", which refers to life different from what we might know already on Earth. The symposium marked the 200th anniversary of the birth of Charles Darwin.
Natural DNA (deoxyribonucleic acid) is the molecule that supports life on Earth. That molecule is built from four building blocks, or "nucleotides". These nucleotides are represented by four letters, A, T, G, and C, where the sequence of those letters in a gene determines what that gene means. When we inherit that information from our parents, DNA is copied according to simple rule (A pairs with T in the double helix, while G pairs with C).
"Darwinian evolution occurs only because natural copies of DNA are imperfect, and because those imperfections themselves can be copied," explained Dr. Benner. "Sometimes the mutations arising from imperfect copying make the child less fit to survive. Sometimes, however, those mutations make the child more fit to survive, especially when the environment is changing. In this case, natural processes select the mutation, and the species as a whole can improve itself to meet new challenges to its survival."
For twenty years now it has been possible to get DNA to evolve in a test tube, Dr. Benner explained. A process known as the "polymerase chain reaction" (of PCR) allows DNA to make copies of itself, and then to have the copies copied, and then to have the copies of the copies copied, and so on. The copying in a PCR is imperfect, and the mistakes cause mutations that themselves can be copied. Therefore, DNA can evolve in a test tube.
The advance reported by FfAME scientists in Chicago involves the application of PCR technology to an artificial synthetic genetic system. The synthetic genetic system was built from six different nucleotides, two more genetic letters than are found in natural DNA. While artificial genetic systems have been described by these scientists previously, the new results showed for the first time that PCR can be done with an indefinite number of unnatural synthetic nucleotides, various mutation processes can occur in the PCR at a low, but significant rate, the artificial genetic alphabet could support replications over dozens of copying cycles, and the reasons for mutations interconverting standard and synthetic nucleotides are understood.
"Scientists are excited about incremental advances," said Dr. Benner. "While genetic alphabets have been examined in the past as binding molecules, and single artificial nucleotides have been incorporated into synthetic genetic systems that have been copied, this is the first time where multiple artificial nucleotides have been so incorporated, where repeated copying with mutation does not lose the artificial nucleotides, and where we understand how we get the mutations that we observe."
Dr. Benner cautioned that this does not mean that synthetic life had been created. Referring to his upcoming book entitled Life, the Universe and the Scientific Method, Dr. Benner listed alternative theories of life, including cell theory, gene theory, and evolutionary theory that underlie the thinking of current biologists about what makes life.
In addition to these, the use of carbon compounds in water, the ability to metabolize those compounds, and the ability to be self sustaining are also considered important or essential to life by many in the biological community.