codon

(noun)

a sequence of three adjacent nucleotides, which encode for a specific amino acid during protein synthesis or translation

Related Terms

Examples of codon in the following topics:

  • Transcription in Prokaryotes

    • The genetic code is a degenerate, non-overlapping set of 64 codons that encodes for 21 amino acids and 3 stop codons.
    • The codons encoding one amino acid may differ in any of their three positions.
    • A codon is made of three nucleotides.
    • Consequently there are 43 (=64) different codons.
    • The 64 codons encode 22 different amino acids and three termination codons, also called stop codons.

  • The Central Dogma: DNA Encodes RNA and RNA Encodes Protein

    • Sixty-one of the codons encode twenty different amino acids.
    • Most of these amino acids can be encoded by more than one codon.
    • These triplets are called stop codons.
    • The codon AUG, also has a special function.
    • The reading frame for translation is set by the AUG start codon.

  • The Mechanism of Protein Synthesis

    • The nucleotides around the AUG indicate whether it is the correct start codon.
    • Once the appropriate AUG is identified, eIF2 hydrolyzes GTP to GDP and powers the delivery of the tRNAi-Met to the start codon, where the tRNAi anticodon basepairs to the AUG codon.
    • The aminoacyl-tRNA with an anticodon complementary to the A site codon lands in the A site.
    • The ribosome translocates once codon on the mRNA.
    • The A site moves over an empty codon, and the process repeats itself until a stop codon is reached.

  • The Initiation Complex and Translation Rate

    • The start codon also establishes the reading frame for the mRNA strand, which is crucial to synthesizing the correct sequence of amino acids.
    • The anticodon on the tRNAi then binds to the start codon via basepairing.
    • Once bound to the mRNA's 5' m7G cap, the 43S complex starts travelling down the mRNA until it reaches the initiation AUG codon at the start of the mRNA's reading frame.
    • Sequences around the AUG may help ensure the correct AUG is used as the initiation codon in the mRNA.
    • The anticodon on tRNAi-Met basepairs with the AUG codon.

  • The Protein Synthesis Machinery

    • Specific tRNAs bind to codons on the mRNA template and add the corresponding amino acid to the polypeptide chain.
    • Of the 61 non-termination codons, one codon (AUG) also encodes the initiation of translation.
    • Each tRNA has a sequence of three nucleotides located in a loop at one end of the molecule that can basepair with an mRNA codon.
    • When the tRNA anticodon basepairs with one of the mRNA codons, the tRNA will add an amino acid to a growing polypeptide chain or terminate translation, according to the genetic code.
    • The opposite end of the folded tRNA has the anticodon loop where the tRNA will basepair to the mRNA codon.

  • Processing of tRNAs and rRNAs

    • The anticodon is a three-nucleotide sequence, unique to each different tRNA, that interacts with a messenger RNA (mRNA) codon through complementary base pairing.
    • The anticodon AAG binds the codon UUC on the mRNA.

  • History of DNA Research

    • Work by Crick and coworkers showed that the genetic code was based on non-overlapping triplets of bases, called codons, and Har Gobind Khorana and others deciphered the genetic code not long afterwards in 1966.

  • Genome Evolution

    • This can result in a shift of reading frame, causing the gene to longer code for the expected protein, a premature stop codon or a mutation in the promoter region.

  • The Evolution of Mitochondria

    • Another possible explanation is that there are differences in codon usage between the nucleus and mitochondria, making it difficult to be able to fully transfer the genes.

  • Types of RNA

    • It then reads the sequence in sets of three bases called codons.