2023-10-12 06:00:05
A recent trial of a new single-cell sequencing technique has unexpectedly changed our understanding of genetic rules.
Image d’illustration Pixabay
Analysis of the genome of a protist has revealed a unique divergence in the DNA code signaling the end of a gene, suggesting the need to continue research to better understand this diverse group of organisms. Dr. Jamie McGowan, a postdoctoral researcher at the Earlham Institute, studied the genomic sequence of a microscopic organism, a protist, taken from a pond (A pond (Latin stagnum) is a body of stagnant, shallow, surface water…) of fresh water in Oxford University Parks. The results were published in the journal PLoS Genetics.
Initially, the objective was to test a DNA sequencing chain capable of working with very small quantities of DNA, such as the DNA of a single cell. Dr. McGowan was collaborating with a team from the Earlham Institute and with Professor Thomas Richards’ group at Oxford University.
However, upon examination of the genetic code, the protist Oligohymenophorea sp. PL0344 turned out to be a novel species, with a surprising change in the way its DNA is translated into proteins. According to Dr. McGowan, the choice of this protist to test their sequencing chain was pure chance, revealing the immensity of what remains to discover, particularly with regard to the genetics of protists.
Protists are difficult to characterize as a group. The majority are single-celled organisms such as amoebae, algae and diatoms, although larger multicellular protists exist. “The definition of a protist is vague. Basically, it is any eukaryotic organism that is neither an animal (An animal (from the Latin animus, spirit, or vital principle) is, according to the classical classification, a… .), nor a plant, nor a fungus,” explains Dr. McGowan, emphasizing the extreme variety of protists.
Oligohymenophorea sp. PL0344 is a ciliate, a swimming protist observable under a microscope, present almost everywhere where there is water. Ciliates have areas of frequent changes in the genetic code, including the reassignment of one or more stop codons—the TAA, TAG, and TGA codons. In almost all organisms, these three stop codons signal the end of a gene.
Credit: Pixabay/CC0 Public Domain
Variations in the genetic code are extremely rare. Among the few variants of the genetic code listed to date, the TAA and TAG codons almost always have the same translation, suggesting that their evolution is coupled.
In Oligohymenophorea sp. PL0344, only TGA functions as a stop codon, although Dr. McGowan found more TGA codons than expected in the ciliate DNA, probably to compensate for the loss of the other two. Instead, TAA specifies lysine and TAG specifies glutamic acid.
Dr. McGowan finds this case “extremely unusual,” calling into question some of the supposed rules of gene translation, illustrating that novel genetic codes can be discovered, intentionally or unintentionally.
More information: Identification of a Non-Canonical Ciliate Nuclear Genetic (Genetics (not to be confused with the Journal of Genetics) is a scientific journal…) Code Where UAA and UAG Code for Different Amino Acids, PLoS Genetics (2023 ). doi.org/10.1371/journal.pgen.1010913
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