Stop codons

Stop codons are sequences of DNA and RNA that signal the end of protein synthesis. They are part of the genetic code, which is used by cells to translate the information in DNA into proteins. There are three stop codons in the standard genetic code: UAA, UAG, and UGA.

Function

Stop codons function to terminate protein synthesis. During translation, the ribosome reads the sequence of codons in the mRNA molecule. When it encounters a stop codon, it releases the newly synthesized protein and disassembles.

Types

There are three stop codons in the standard genetic code: UAA, UAG, and UGA. These are also known as "nonsense" codons, because they do not code for an amino acid. Instead, they signal the end of the protein chain.

Role in disease

Mutations that change a normal codon into a stop codon can cause disease by prematurely terminating protein synthesis. This results in a truncated, and often nonfunctional, protein. Such mutations are known as nonsense mutations.

See also

• Start codon
• Codon
• Genetic code
• Translation (biology)

References

Stop codons Resources
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