The genetic code is the set of rules by which information stored in DNA and RNA is translated into proteins. Proteins are composed of long chains of amino acids, and the genetic code determines the sequence of amino acids that are assembled to form a particular protein.
The genetic code is made up of a series of codons, which are sequences of three nucleotides (the building blocks of DNA and RNA) that specify a particular amino acid or a stop signal. There are 64 possible codons, which can code for the 20 different amino acids found in proteins as well as the stop signal that terminates protein synthesis. The genetic code is universal, meaning that it is the same in all organisms, from bacteria to humans.
The genetic code is degenerate, meaning that more than one codon can code for the same amino acid. For example, the codons GGU, GGC, GGA, and GGG all code for the amino acid glycine. However, some amino acids are specified by only one codon, such as methionine (AUG) and tryptophan (UGG).
The genetic code also has specific start and stop codons that mark the beginning and end of the protein-coding sequence. The start codon is AUG, which codes for methionine, and serves as the initiation signal for protein synthesis. The stop codons are UAA, UAG, and UGA, which do not code for amino acids but instead signal the end of the protein-coding sequence.
The genetic code is redundant, meaning that changes in the third nucleotide of a codon (the “wobble” position) often do not change the amino acid that is coded for. This allows for some tolerance of mutations in the DNA sequence without affecting the final protein product.
Overall, the genetic code is a fundamental aspect of molecular biology that underlies the process of protein synthesis and the expression of genetic information in all living organisms. Its universality and redundancy provide a robust system for encoding and decoding genetic information.