After our long and laborious genetics unit, we learned that DNA is the most advanced form of genetic material, most likely evolving from RNA. But RNA is much too complex, requiring many enzymes and serving multiple functions, to be considered the most basic form of genetic code. Scientists have been very confused over the origins of the genetic code until recently. With new research originating from Arizona State University’s Biodesign Institute, scientists have pinpointed a suitable candidate for RNA’s baby daddy. Threose nucleic acid, TNA, is a much simpler form of genetic code that can easily be transcribed into RNA, or even directly transcribed into DNA, with commercially available enzymes.
TNA is considered to be much simpler than RNA due to its ability to be synthesized from a single starting material. Unlike RNA or DNA it does not require primers, multiple versions of polymerase or auxiliary enzymes such as ligase and helicase. Additionally, TNA has a sugar backbone containing only four carbons unlike the traditional 5 carbon RNA and DNA backbones. Because of this the TNA can be made from just two identical carbon units. This, along with the lack of enzymes needed to form TNA makes it far easier and more likely for TNA to have formed in the probiotic soup of early earth.
Some may argue that the differences in TNA and RNA or DNA are enough to prove that TNA cannot be the precursor of more complex forms of genetic code. However, using in vitro tests, scientists were able to transcribe the TNA equivalent of genes found in DNA that code for clotting proteins. This proves that the bridge between TNA and current forms of genetic code can be crossed with traditional transcription biological machinery.
The discovery of TNA has enlightened many fields of study in unforeseen ways. For example, exobiologists, scientists searching for alternative life forms elsewhere in the universe, have been able to add TNA to the library of molecules they look for that may signify the possibility of life. In the field of biomedicine, TNA and other preliminary genetic molecules can be used to artificially make proteins or other polymers lacking in the patient’s body. Because TNA is resistant to nuclease degradation it can be a more reliable alternative to damaged DNA in humans.
Research on TNA is still under appreciated, but one thing can be said for sure: regardless of whether or not it truly is the first primitive genetic code of life, its discovery will continue to shape biotechnology for decades to come.
For more information, check out the links below: