Stop codons are nucleic acid triplets in DNA and mRNA that signal the end of protein production. They prevent endless chains of amino acids and reduce the risk of mistakes. Mutations in stop codons can cause cell malfunction or congenital mutations. Geneticists use stop codons to identify specific amino acid chains and learn more about genetic material.
A stop codon is a nucleic acid triplet in messenger RNA (mRNA) that does not code for an amino acid, thus stopping the production of a protein. Essentially, the stop codon tells the ribosomes that execute the mRNA code that it’s time to stop; one could almost think of it as a perforated line in a sheet of paper indicating “tear here”. Without a stop codon, the proteins made from RNA would consist of endless chains of amino acids, because the ribosomes wouldn’t know when to stop.
Stop codons are also present in DNA, so they are transported when DNA is transcribed into RNA. In DNA, the three stop codons are TAA, TAG and TGA. These triplets are “nonsense” codons that encode nothing, reducing the risk of a mistake being made. When transcribed into RNA, the stop codons are UAA, UAG and UGA.
The length of an amino acid chain in a protein can vary, meaning that stop codons are found at varying intervals in the coding of DNA and RNA, the areas of the genetic code that contain information that must be executed to make proteins . Stop codons can be identified when DNA is sequenced and can be used to identify specific locations in the genetic code that correspond to particular proteins, and therefore to particular genetic information.
As with other areas of DNA, it is possible for a mutation to appear in a stop codon. The codon can be transcribed incorrectly or the nucleic acids in the codon can be swapped, causing problems when ribosomes go about translating mRNA to build chains of amino acids. In a single cell, this can result in a random mutation causing the cell to die or malfunction. If stop codon errors occur in a germ cell, however, and that germ cell joins one from another organism, the resulting organism will have a congenital mutation, and in some cases, the mutation can be so severe that the organism cannot live.
Geneticists can use their knowledge of stop codons to order information in a piece of DNA or RNA. By looking for stop codons, they can identify specific amino acid chains and determine which proteins the genetic material is coding for. This information can be used to learn more about what it does and what happens when it goes wrong. Finding a stop codon can be useful when studying DNA and RNA to learn more about an identified mutation or variation.
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