Cellular RNA Imaging: Numerous techniques have been developed for imaging RNA, and in parallel super resolution and single-molecule techniques have allowed high-resolution imaging of biomolecules in cells. In this review, we highlight curr...
Reflections on the Origin and Early Evolution of the Genetic Code
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A primordial anti-messenger RNA composed only of adenosine and uracil nucleotides is proposed 1) to contain anticodons for a maximum of eight different amino acids (left) and, consequently, be able to form short active polypeptides and 2) to fold as a hairpin RNA adaptor exposing one of the anticodons for the formation of a specific amino acyl species (right).
Examination of the genetic code (GeCo) reveals that amino acids coded by (A/U) codons display a large functional spectrum and bind RNA whereas, except for Arg, those coded by (G/C) codons do not. From a stereochemical viewpoint, the clear preference for (A/U)-rich codons to be located at the GeCo half blocks suggests they were specifically determined. Conversely, the overall lower affinity of cognate amino acids for their (G/C)-rich anticodons points to their late arrival to the GeCo. It is proposed that i) initially the code was composed of the eight (A/U) codons; ii) these codons were duplicated when G/C nucleotides were added to their wobble positions, and three new codons with G/C in their first position were incorporated; and iii) a combination of A/U and G/C nucleotides progressively generated the remaining codons.Zum Volltext
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