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The genetic code is the set of rules used by living cells to translate ... Efforts to understand how proteins are encoded began after DNA's structure was discovered ...
George Gamow suggested that the genetic code was made of three nucleotides per amino acid. He reasoned that because there are 20 amino acids and only four bases, the coding units could not be single (4 combinations) or pairs (only 16 combinations). Rather, he thought triplets (64 possible combinations) were the coding unit of the genetic code.
When DNA is transcribed to RNA, its complement is paired to it. DNA codes are transferred to RNA codes in a complementary fashion. The encoding of proteins is done in groups of three, known as codons. The standard codon table applies for humans and mammals, but some other lifeforms (including human mitochondria [9]) use different translations. [10]
Four novel alternative genetic codes were discovered in bacterial genomes by Shulgina and Eddy using their codon assignment software Codetta, and validated by analysis of tRNA anticodons and identity elements; [3] these codes are not currently adopted at NCBI, but are numbered here 34-37, and specified in the table below.
In 1960, Jacob and collaborators discovered the operon which consists of a sequence of genes whose expression is coordinated by operator DNA. [27] In the period 1961 – 1967, through work in several different labs, the nature of the genetic code was determined (e.g. [28]).
The Crick, Brenner et al. experiment (1961) was a scientific experiment performed by Francis Crick, Sydney Brenner, Leslie Barnett and R.J. Watts-Tobin. It was a key experiment in the development of what is now known as molecular biology and led to a publication entitled "The General Nature of the Genetic Code for Proteins" and according to the historian of Science Horace Judson is "regarded ...
It was discovered that the cell uses DNA as a template to create matching messenger RNA, molecules with nucleotides very similar to DNA. The nucleotide sequence of a messenger RNA is used to create an amino acid sequence in protein; this translation between nucleotide sequences and amino acid sequences is known as the genetic code. [36]
The definition normally excludes regions of the genome that control transcription but are not themselves transcribed. We will encounter some exceptions to our definition of a gene - surprisingly, there is no definition that is entirely satisfactory. [16] A gene is a DNA sequence that codes for a diffusible product.