No one knows the origin of the genetic code for DNA/RNA observed in all living organisms on Earth. Current scientific thinking is that the genetic code evolved naturally during the abiogenic origin of life from random combinations of atoms and molecules following the known laws of physics. But could the genetic code have been built into the Big Bang, coded into atoms, and spread throughout the universe through radioactive decay processes? Could this genetic-code-in-big-bang hypothesis be experimentally tested?
I would very strongly doubt that. The genetic code is determined by which amino acid is loaded onto which tRNA, not by the intrinsic biophysical properties of the different nucleotide triplets. And this, in turn, is determined by the specific AAtRNA synthases that catalyse this loading process.
In the lab, it is possible to manipulate the code, e.g. by altering the recognition triplet in the tRNA to that of another amino acid or to one of the stop codons, by altering the specificity of the AAtRNA synthases or chemically loading the "wrong" amino acids to a rarely used tRNA.
This can be used to introduce non-natural amino acids into proteins by, for example, in vitro loading different amino acids to particular tRNAs, which then lead to the introduction of these amino acid. Since the genetic code is highly degenerate, using 64 codons to encode 20 amino acids and the stop signal, and in some bacteria, some codons are used very rarely or not at all, these rarely-used codons can be targeted to expand the genetic code in these bacteria to biosynthetically produce proteins containing non-natural amino acids.
See: https://en.wikipedia.org/wiki/Expanded_genetic_code#:~:text=An%20expanded%20genetic%20code%20is,naturally%2Dencoded%20proteinogenic%20amino%20acids.
and the publications cited therein.
Hello Annemarie,
What you said applies to the FUNCTION of DNA, tRNA, AAtRNA synthases etc, and not to their ORIGINs, which remain a deep mystery. Francis Crick, one of the discoverers of the genetic code, wrote that "an honest man, armed with all the knowledge available to us now, could only state that in some sense, the origin of life appears at the moment to be almost a miracle, so many are the conditions which would have had to have been satisfied to get it going." (Life Itself: Its Origin and Nature, 1981, p. 88. The microvita hypothesis proposes that DNA/RNA information and the genetic code are contained in atoms and are released through radioactivity, and that this can be tested experimentally. If the test comes out positive, the question then becomes, how did atoms, some of whose nuclei are formed seconds after the beginning of the Big Bang, come to encode this information?
The Big Bang produced matter mainly in the form of hydrogen and helium. The heavier elements essential for the formation of biomolecules, such as carbon, oxygen, nitrogen and phosphorus were produced only as the first generation of stars approached the end of their lifespan: see https://svs.gsfc.nasa.gov/13873 "The origin of the elements". The information needed for intermolecular interactions is not contained in the isolated atoms, but in the perturbations of the electron orbitals caused by a specific spacial arrangement of the atoms, which in turn is the result of intramolecular electron interactions. Genetic information is definitely not "released through radioactivity" - chemical processes in general, including biochemical processes, are phenomena of the electron shell of atoms and molecules, not nuclear processes, and different isotopes of the same element that may vary widely in their nuclear stability and therefore their radioactivity have roughly the same chemical properties.
The DNA/RNA genetic code, a complex genetic instructions used in the development and functioning of all known living organisms and many viruses. Within the context of the early stages of the Big Bang, which occurred nearly 13.8 billion years ago, the existence of such complex molecules would have been highly unlikely. The Big Bang initiated a rapidly expanding and extremely hot universe, which is primarily filled with simple sub-atomic particles and radiation, not conducive to the formation of complex molecules. As the universe cooled and expanded, simple atoms like "H" and 'He" formed, eventually leading to the synthesis of more complex elements through stellar processes. It was only much later in the cosmic timeline, within the cooler and more stable environments of forming planetary systems, that complex molecules, including organic compounds necessary for life as we know it, could have formed. Therefore, the DNA/RNA genetic code, would not have been present during the early stages of the Big Bang but emerged much later in the evolutionary history of the universe.
- Badges
- Science method
- Similar topics
- Biological Science
- Histology
- Staining