Recent developments in microorganism studies has suggested that the genetic codes flexibility may be greater than previously thought. A new study by researchers from the U.S Department of Energy Joint Genome Institute (DOE JGI) and Yale University has discovered that the codon for the amino acid selenocysteine is not coherent across all organisms. Scientists found that in some microorganisms, the three-letter codon UGA signals for the translation of the amino acid selenocysteine. This is of major significance because UGA is among three codons that normally signal the termination of protein construction.

Starting from the four innermost letters and working to the outermost ring, this table shows shows which three-letter base sequence or codon encodes which amino acid. Credit: Wikimedia Commons, public domain image


Researchers scanned approximately 6.4 trillion bases of metagenomic sequence and 25,000 microbial genomes in the National Center for Biotechnology Information and the DOE JGI's Integrated Microbial Genomes data management system. Based on two 2014 publications in the journal Science, they expected to find variations in microorganisms genetic vocabulary within nature. The team discovered several species that identify stop codons UGA, UAG and UAA, as well as ten sense codons, that are variants for selenocysteine.

This finding is of major significance because it is opening geneticist's minds to the possibility of a greater network of genetic schemes. While our knowledge of genetics has grown tremendously over the past couple of decades, there remains an abundance of questions unanswered about the intricacies between reading the genetic code and applying it. The genetic variation in microorganisms is far greater than in animal species and the further study of these microorganisms may prove useful to fill in the missing gaps of our current genetic knowledge.

Differences Among Coding for Amino Acids

It has been stressed that DNA codes for amino acids. For any of the 64 codons, or combination of three bases, there is a specified amino acid. Previously, it was believed that this language was universal for all organisms, as show in laboratory generations.  However, the U.S. Department of Energy Joint Genome Institution found that for uncultivated microbes codons differ in the amino acid they inscribe. The study zoned in on the three stop codons, UAA, UGA and UAG where the chain then terminates.

It was found that in other organisms the stop codons actually code for an amino acid, thus the chain continues. The research led by Eddy Rubin concluded that each of these three codons have been reassigned in various ways. For instance, Bacteria and Eukaryotas each redefined a different stop codon. Archaea showed no change to these three codons. This data builds on unexplored areas within the tree of life.

I found this article interesting as it related to the evaluation of all life on a microscopic level. Research within DNA has only increased in popularity , thus the differences among organisms is foretelling to our past. How do our codes for amino acids differ and why? Are some of these stop codons not essential to life or only fundamental for certain organisms? This study opens up question and reasoning for evolution of life.

The article can be found here.