Protein synthesis

• Protein synthesis occurs in the ribosome, which is outside of the nucleus.

  But, since the DNA is such a big structure, it can't leave through the tiny holes in the nucleus membrane.

  So instead, it creates a copy of the gene, which will be small enough to leave through the holes.

  This copy is called mRNA (messenger RNA).

  For the mRNA to be made the DNA has to be separated (not in double helix).
• The mRNA;

  • It is a copy of a gene from the nucleus, which travels to the ribosomes, for protein synthesis.
  • The mRNA will be complementary to DNA. So if DNA is C, mRNA is G ect.
  • Important DIFFERENCES:
  • It is much shorter than DNA.
  • It is only a single strand.
  • Instead of the T (thymine) base, it contains uracil. The uracil will pair with the A base.
• Template strand is what is used to make complementary mRNA.
• Every 3 bases (triplet/codon) codes for a specific amino acid.
• Once mRNA arrives at ribosome:

  • tRNA (transfer RNA) bring one amino acid to the ribosome.
  • The tRNA have the amino acid at the top and the anti-codon at the bottom. The anti-codon is complimentary to the bases on the mRNA.
  • tRNA make sure that the correct amino acid is made and given in the correct order to ribosome.
  • Once all amino acids are made, it folds up on itself to form a protein.
• How amino acid sequence is assembles using a DNA base sequence;

  • A single strand of mRNA is transcribed from the gene in the nucleus, by making the DNA sequence to separate.
  • mRNA leaves the nucleus and binds to ribosome.
  • The triplet code from the mRNA is matched by the complementary tRNA anticodon at the ribsomose.
  • tRNA transfers amino acids in a specific order to make a protein.