Genetic code
Channel: 宇宙のすべての知識 プリンシピア
Date: 2019-02-14

Genetic code, by Wikipedia https://en.wikipedia.org/wiki?curid=12385 / CC BY SA 3.0

#Gene_expression
#Genetics
#Molecular_genetics
#Molecular_biology
#Protein_biosynthesis
Genetic code

The genetic code is the set of rules used by living cells to translate information encoded within genetic material (DNA or mRNA sequences) into proteins. Translation is accomplished by the ribosome, which links 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.

The code defines how sequences of nucleotide triplets, called "codons", specify which amino acid will be added next during protein synthesis. With some exceptions, a three-nucleotide codon in a nucleic acid sequence specifies a single amino acid. The vast majority of genes are encoded with a single scheme (see the RNA codon table). That scheme is often referred to as the canonical or standard genetic code, or simply "the" genetic code, though variant codes (such as in human mitochondria) exist.

While the "genetic code" determines a protein's amino acid sequence, other genomic regions determine when and where these proteins are produced according to various "gene regulatory codes".

Efforts to understand how proteins are encoded began after DNA's structure was discovered in 1953. George Gamow postulated that sets of three bases must be employed to encode the 20 standard amino acids used by living cells to build proteins, which would allow a maximum of 64 amino acids.

The Crick, Brenner, Barnett and Watts-Tobin experiment first demonstrated that codons consist of three DNA bases. Marshall Nirenberg and Heinrich J. Matthaei were the first to reveal the nature of a codon in 1961.

They used a cell-free system to translate a poly-uracil RNA sequence (i.e., UUUUU...) and discovered that the polypeptide that...