Translation Turns mRNA to Polypeptides
Definition
Translation
Translation is the synthesis of polypeptides from mRNA, where the base sequence of mRNA is converted into an amino acid sequence.
- The genetic code uses codons (triplets of bases on mRNA), each specifying an amino acid or start/stop signal.
- tRNA molecules deliver amino acids to the ribosome by matching their anticodons with complementary codons on mRNA through base pairing.
- The ribosome reads the mRNA and assembles amino acids into a polypeptide chain.
The Process of Translation
The key players of translation are mRNA, ribosomes, and tRNA.
1. Initiation
- The small ribosomal subunit binds to the mRNA near the start codon (AUG).
- A tRNA carrying methionine pairs its anticodon (UAC) with the start codon.
- The large ribosomal subunit attaches, forming a complete ribosome.
2. Elongation
- A tRNA with the next amino acid binds to the A site of the ribosome.
- A peptide bond forms between the amino acids, linking them together.
- The ribosome shifts one codon along the mRNA:
- The tRNA in the P site moves to the E site and exits.
- The tRNA in the A site moves to the P site.
- The A site is now open for the next tRNA.
- This process repeats, adding one amino acid at a time to the growing polypeptide chain.
3. Termination
- When a stop codon (UAA, UAG, or UGA) reaches the A site, no tRNA can bind.
- Release factors bind to the ribosome, prompting it to release the completed polypeptide.
- The ribosome disassembles.
- The base sequence of mRNA is translated into the amino acid sequence of a polypeptide through complementary base pairing between mRNA codons and tRNA anticodons.
- The ribosome reads the mRNA one codon at a time, assembling amino acids in the correct sequence to build the polypeptide.
- Which ribosomal unit does initiation occur on?
- What kind of bond forms between amino acids during elongation?
- What happens at the end of termination?
