What is the definition for codon recognition?
Codon recognition refers to the process by which a specific codon on a messenger RNA (mRNA) molecule is recognized and matched with the appropriate transfer RNA (tRNA) molecule during protein synthesis. This recognition occurs in the ribosome, the molecular machinery responsible for translating the mRNA sequence into a specific amino acid sequence.
To understand the definition of codon recognition, it is helpful to know the following steps:
1. Transcription: The process in which the DNA sequence is transcribed into an mRNA molecule.
2. Translation: The process in which the mRNA sequence is translated into a protein sequence.
3. Codons: A codon is a three-nucleotide sequence on the mRNA molecule that encodes for a specific amino acid. For example, the codon AUG codes for the amino acid methionine, which is often the start codon.
4. tRNA: Transfer RNA molecules carry specific amino acids to the ribosome during translation. Each tRNA molecule binds to a specific codon on the mRNA through its anticodon, a three-nucleotide sequence complementary to the codon.
Now, let's look at how codon recognition takes place:
1. Initiation: The ribosome recognizes and attaches to the mRNA molecule at the start codon. In eukaryotes, this is usually the AUG codon.
2. Matching tRNA: The appropriate tRNA molecule with an anticodon complementary to the codon on the mRNA binds to the ribosome.
3. Peptide bond formation: The ribosome catalyzes the formation of a peptide bond between the amino acid carried by the tRNA and the growing polypeptide chain.
4. Translocation: The ribosome moves along the mRNA molecule, shifting to the next codon. This process exposes a new codon for codon recognition.
5. Elongation: Steps 2-4 repeat, adding new amino acids to the growing polypeptide chain until a stop codon is encountered.
6. Termination: The ribosome reaches a stop codon, and the polypeptide chain is released. Protein synthesis is complete.
In summary, codon recognition refers to the recognition and binding of a specific codon on the mRNA molecule by a corresponding tRNA molecule, ensuring the accurate translation of the mRNA sequence into a polypeptide chain during protein synthesis.