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How to translate DNA?

Published in Protein Synthesis 3 mins read

Translation isn't directly from DNA, but rather from RNA which is transcribed from DNA; translation is the process of using RNA to synthesize a sequence of amino acids to form a polypeptide (or protein). This process relies on the information encoded in messenger RNA (mRNA) to build a protein.

Understanding Translation: From RNA to Protein

Translation is a vital step in gene expression where the genetic code carried by mRNA is decoded to produce a specific amino acid chain, which later folds into an active protein. According to the provided reference, "Translation is the process of using RNA to synthesize a sequence of amino acids to form a polypeptide (or protein)."

The Key Players in Translation

  • mRNA (messenger RNA): Carries the genetic code from DNA to the ribosome. Each set of three nucleotides (a codon) in mRNA specifies a particular amino acid.

  • Ribosomes: The protein synthesis machinery. Ribosomes bind to mRNA and use the codons to direct the assembly of amino acids.

  • tRNA (transfer RNA): Acts as an adapter molecule. Each tRNA molecule carries a specific amino acid and has an anticodon region that complements a specific mRNA codon. This ensures the correct amino acid is added to the growing polypeptide chain.

The Steps of Translation

While the exact steps have many complexities, here is a simplified overview:

  1. Initiation: The ribosome binds to the mRNA at a specific start codon (usually AUG). A tRNA carrying the corresponding amino acid (methionine in eukaryotes) binds to the start codon.

  2. Elongation: The ribosome moves along the mRNA, codon by codon. For each codon, a tRNA with the complementary anticodon brings the corresponding amino acid. The amino acid is added to the growing polypeptide chain through the formation of a peptide bond.

  3. Translocation: After a new amino acid has been added to the polypeptide chain, the ribosome moves down the mRNA by one codon, allowing a new tRNA to bind and add its amino acid.

  4. Termination: The ribosome encounters a stop codon (UAA, UAG, or UGA) on the mRNA. There are no tRNAs that recognize these codons. Instead, release factors bind to the ribosome, causing the polypeptide chain to be released and the ribosome to dissociate.

Example

Imagine an mRNA sequence: AUG-GCA-UAC-UGA.

  • AUG is the start codon, signaling the beginning of translation and coding for methionine.
  • GCA codes for alanine.
  • UAC codes for tyrosine.
  • UGA is a stop codon, signaling the end of translation.

The resulting polypeptide sequence would be methionine-alanine-tyrosine.

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