protein synthesis

• Transcription is when DNA is transcribed and an mRNA molecule is produced.
• Translation is when mRNA (messenger RNA) is translated and an amino acid sequence is produced.
• The shape of a protein is determined by the sequence of amino acids. The sequence of amino acids is determined by the sequence of nucleotides in the gene encoding it.
• Transcription:

  1. Part of DNA molecule unwinds and exposes the gene to be transcribed.
  2. RNA polymerase binds to a region of non-coding DNA in front of the gene.
  3. RNA polymerase makes a complementary copy of the code from the gene and makes mRNA.
  4. mRNA leaves nucleus via pore in nuclear envelope.
• Translation:

  1. After leaving the nucleus, the mRNA molecule attaches to a ribosome.
  2. The ribosome ‘reads’ the code on the mRNA in groups of three (colons).
  3. The ribosome translates the sequence of bases into a sequence of amino acids that make up a protein.
• mRNA:

  • Shorter than DNA.

  • Contains 4 nucleotides with the nitrogenous bases: A, C, G & U (Uracil)

  • Single stranded.