Biology: Translation in Protein Synthesis

Translation

• Translation is the process by which genetic information encoded in mRNA is used to synthesize proteins.
• This process takes place in the ribosomes, which are the cellular structures responsible for protein synthesis.
• Translation is the second step in the central dogma of molecular biology.

Stages of Translation

• Initiation: mRNA binding, start codon recognition, tRNA binding, and formation of initiation complex.
  • mRNA binding: The small subunit of the ribosome binds to the mRNA near its 5’ end.
  • Start codon recognition: The start codon (AUG) on the mRNA is recognized, which codes for the amino acid methionine.
  • tRNA binding: A specific initiator tRNA carrying methionine binds to the start codon through complementary base pairing.
  • Formation of initiation complex: The large subunit of the ribosome joins the small subunit, forming the complete ribosome and initiating the translation process.

Elongation

• Codon recognition: The ribosome moves along the mRNA, and each codon on the mRNA is recognized by a corresponding tRNA carrying the appropriate amino acid.
• Peptide bond formation: The ribosome facilitates the formation of a peptide bond between the amino acid carried by the tRNA in the P site and the amino acid carried by the tRNA in the A site.
• Translocation: The ribosome moves one codon down the mRNA, shifting the tRNA with the growing polypeptide chain to the P site and the now empty tRNA to the E site.

Termination

• Stop codon recognition: Translation continues until the ribosome encounters a stop codon (UAA, UAG, or UGA) on the mRNA.
• Release of polypeptide: Release factors bind to the ribosome at the stop codon, prompting the release of the completed polypeptide chain from the tRNA in the P site.
• Disassembly of ribosome: The ribosomal subunits, mRNA, and release factors dissociate, freeing the newly synthesized protein and allowing the ribosomal subunits to be reused for another round of translation.

Components

• mRNA: Carries the genetic code from DNA, specifying the sequence of amino acids in the protein.
• tRNA: Transfer RNA molecules bring the appropriate amino acids to the ribosome, each with an anticodon that pairs with a specific mRNA codon.
• Ribosome: The molecular machine that facilitates the synthesis of proteins, composed of rRNA and proteins, with three binding sites for tRNA: A site, P site, and E site.
• Aminoacyl-tRNA synthetase: Enzymes that attach the correct amino acid to its corresponding tRNA.
• Initiation, elongation, and release factors: Proteins that assist in the various stages of translation.

Codons

• Codons: A sequence of three nucleotides on the mRNA that corresponds to a specific amino acid or a stop signal.
• There are 64 possible codons.
• Redundancy: Multiple codons can code for the same amino acid, providing some tolerance for mutations.
• Start codon: AUG, which codes for methionine and signals the start of translation.
• Stop codons: UAA, UAG, and UGA, which signal the end of translation.

This quiz covers the process of translation, where genetic information in mRNA is used to synthesize proteins in ribosomes. It's the second step in the central dogma of molecular biology.