Protein Synthesis

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  • Created by: zoolouise
  • Created on: 24-05-16 15:41
  • Transcription is where one strand of the DNA acts as a template for the production of mRNA, a complementary section of part of the DNA sequence. This occurs in the nucleus.
  • Translation is where the mRNA acts as a template to which complementary tRNA molecules attach, and the amino acids they carry are linked to form a polypeptide. This occurs on the ribosomes in the cytoplasm.


DNA doesn't leave the nucleus. Transcription is the process whereby part of the DNA, the gene, acts as a template for the production of mRNA, which carries information needed for protein synthesis from the nucleus to the cytoplasm. Ribosomes in the cytoplasm provide a suitable surface for the attachment of mRNA and the assembly of protein. This is the sequence of events:

  • The enzyme DNA helicase breaks the hydrogen bonds between the bases in a specific region of the DNA molecule, causing the two strands to separate and unwind, exposing the nucleotide bases.
  • The enzyme RNA polymerase binds to the template strand of the DNA at the beginning of the sequence to be copied.
  • Free RNA nucleotides align opposite the template strand, based on the complementary relationship between the bases in DNA and the free nucleotides. 
  • RNA polymerase moves along the DNA forming bonds that add RNA nucleotides, one at a time, to the growing RNA strand. This results in the synthesis of a molecule of MRNA alongside the unwound portion of DNA. Behind…


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