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Protein Synthesis

PROTEIN SYNTHESIS

The genetic information stored in DNA is transcribed into mRNA and then transformed into protein.

Transcription

  1. Sigma factors enable RNA polymerase to bind to promoter DNA.
  2. TRNA polymerase allows the DNA to untwist then unzips, the hydrogen bonds between complementary DNA nucleotides break
  3. Free RNA nucleotides form complementary base pairs with one DNA strand (Template/ sense strand)

The unused strand is named the Antisense / coding strand – b/c it has the same coding as the mRNA

  1. Weak hydrogen bonds form between base pairs
  2. Sugar phosphate bonds form between RNA nucleotides
  3. mRNA strand is synthesized
  4. Hydrogen bonds of the untwisted RNA + DNA helix break, freeing the newly synthesized RNA strand.
  5. mRNA peels off the DNA and is small enough to move out of the nuclear pores into the cytoplasm

Translation

Translation takes place on the ribosome’s in the cytoplasm – the ribosome’s are the sites of protein synthesis

  1. The mRNA strand attaches to a ribosome and passes along it in short spurts of 3 nucleotides at a time so that it can be “read”.
  2. Each mRNA codon codes for a specific amino acid
  3. mRNA is decoded by a ribosome complex and signals are sent to induce the binding of tRNA to mRNA
  4. tRNA molecules transport specific amino acids to the ribosome that are chained together into a polypeptide
  5. The anti-codons in tRNA and codons in mRNA match up and form complementary base pairs
  6. Peptide bonds form between the adjacent amino acids to form the polypeptide (protein)
  7. A stop codon is finally met so the ribosomal complex falls apart and the protein is released into the cell
  8. tRNA is reused and collects another specific amino acid e.g. broken down into free nucleotides to be reused.