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For translation, each of these codons requires a tRNA molecule with an anticodon with which it can stably complement. If each tRNA molecule is paired with its complementary mRNA codon using canonical Watson-Crick base pairing, then 64 types of tRNA molecule would be required.
A codon table can be used to translate a genetic code into a sequence of amino acids. [1] [2] The standard genetic code is traditionally represented as an RNA codon table, because when proteins are made in a cell by ribosomes, it is messenger RNA (mRNA) that directs protein synthesis. [2] [3] The mRNA sequence is determined by the sequence of ...
An anticodon [16] is a unit of three nucleotides corresponding to the three bases of an mRNA codon. Each tRNA has a distinct anticodon triplet sequence that can form 3 complementary base pairs to one or more codons for an amino acid. Some anticodons pair with more than one codon due to wobble base pairing.
Translation is accomplished by the ribosome, which links proteinogenic amino acids in an order specified by messenger RNA (mRNA), using transfer RNA (tRNA) molecules to carry amino acids and to read the mRNA three nucleotides at a time. The genetic code is highly similar among all organisms and can be expressed in a simple table with 64 entries.
They are the aminoacyl site (abbreviated A), and the peptidyl site/ exit site (abbreviated P/E). Concerning the mRNA, the three sites are oriented 5' to 3' E-P-A, because ribosomes move toward the 3' end of mRNA. The A-site binds the incoming tRNA with the complementary codon on the mRNA. The P/E-site holds the tRNA with the growing polypeptide ...
It is notable in this context, that the Wobble hypothesis of Francis Crick predicted the possibility of G:U base pair, in place of the canonical G:C or A:U base pairs, also mediating the recognition between mRNA codons and tRNA anticodons, during protein synthesis. The G:U wobble base pair is the most numerously observed non-canonical base pair.
The tRNA recognizes a specific three nucleotide codon in the mRNA with a complementary sequence called the anticodon on one of its loops. Each three-nucleotide codon is translated into one of twenty naturally occurring amino acids. [6] There is at least one tRNA for any codon, and sometimes multiple codons code for the same amino acid.
For example, if the amino acid that attach to the end is phenylalanine, the reaction will be catalyzed by phenylalanine-tRNA synthase to produce tRNA phe. [4] The other end—the bottom often called the "DNA arm"—consists of a three base sequence that pairs with a complementary base sequence in a mRNA. [5]