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[2] [3] The mRNA sequence is determined by the sequence of genomic DNA. [4] In this context, the standard genetic code is referred to as 'translation table 1' among other tables. [3] It can also be represented in a DNA codon table. The DNA codons in such tables occur on the sense DNA strand and are arranged in a 5 ′-to-3 ′ direction.
Alternative start codons are different from the standard AUG codon and are found in both prokaryotes (bacteria and archaea) and eukaryotes. Alternate start codons are still translated as Met when they are at the start of a protein (even if the codon encodes a different amino acid otherwise). This is because a separate tRNA is used for ...
A The codon AUG both codes for methionine and serves as an initiation site: the first AUG in an mRNA's coding region is where translation into protein begins. [ 7 ] Differences from the standard code
The most common start codon is AUG, which is read as methionine or as formylmethionine (in bacteria, mitochondria, and plastids). Alternative start codons depending on the organism include "GUG" or "UUG"; these codons normally represent valine and leucine, respectively, but as start codons they are translated as methionine or formylmethionine. [33]
The AUG is the initiation codon encoding a methionine amino acid at the N-terminus of the protein. (Rarely, GUG is used as an initiation codon, but methionine is still the first amino acid as it is the met-tRNA in the initiation complex that binds to the mRNA). Variation within the Kozak sequence alters the "strength" thereof.
Proteins are translated by reading tri-nucleotides on the mRNA strand, also known as codons, from one end of the mRNA to the other (from the 5' to the 3' end) starting with the amino acid methionine as the start (initiation) codon AUG. Each codon is translated into a single amino acid.
Eukaryotic mRNA precursors must be processed in the nucleus (e.g., capping, polyadenylation, splicing) in ribosomes before they are exported to the cytoplasm for translation. Translation can also be affected by ribosomal pausing, which can trigger endonucleolytic attack of the tRNA, a process termed mRNA no-go decay. Ribosomal pausing also aids ...
For example, all three positions of methionine's AUG are non-degenerate, because the only codon coding for methionine is AUG. The same goes for tryptophan's UGG. [2]: 521–522 There are three amino acids encoded by six different codons: serine, leucine, and arginine. Only two amino acids are specified by a single codon each.