Translation and splicing of RNA to produce proteins

Translation and splicing of RNA to produce proteins

Translation of RNA to Proteins

Overview

  • The process of translation involves converting the information in mRNA into a sequence of amino acids to produce proteins.
  • It occurs in the ribosomes of the cell, located in the cytoplasm.

Stage 1: Initiation

  • The ribosome attaches to the start codon (AUG) on an mRNA molecule.
  • A transfer RNA (tRNA) molecule that complements the start codon, carrying a specific amino acid (methionine in eukaryotes), binds to the mRNA.

Stage 2: Elongation

  • A second tRNA molecule, carrying a different amino acid and a complementary anticodon to the next codon on the mRNA, attaches to the adjacent binding site.
  • The ribosome aids the formation of a peptide bond between the two amino acids, detaching the first tRNA.
  • The ribosome moves along the mRNA, repeating this process until it reaches a stop codon.

Stage 3: Termination

  • Once a stop codon is reached, the process of translation ends.
  • The polypeptide chain formed during translation folds into a protein.
  • The mRNA and the last tRNA molecule detach from the ribosome.

Post-Translation Modification

  • The newly formed polypeptide chain undergoes various modifications to become a functional protein.
  • Certain amino acids might be chemically modified, extraneous sequences might be removed, and the protein might be folded into its required shape.
  • Some proteins also have carbohydrates added or are sent to the Golgi apparatus for further modifications.

Splicing of RNA

Overview

  • Removal of non-coding sequences (introns) from the primary transcript or pre-mRNA is known as splicing.
  • It happens in the nucleus of eukaryotic cells before the mRNA is transported to the cytoplasm.

Splicing Process

  • The introns are looped out and cut off by a complex of proteins and small nuclear RNAs, called the spliceosome.
  • The coding sequences or exons are then joined together to form the final mRNA molecule.
  • It enables one gene to produce different proteins, depending on which exons are included or excluded, increasing protein diversity.

Significance

  • The various processes involved in gene expression, including transcription, splicing, translation, and post-translation modification, allow the cell to make a wide range of proteins needed for its specific functions.
  • Errors in any of these stages could lead to the production of faulty proteins, having implications for health and diseases.