F215 Cellular Control

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Cellular Control
- DNA and Proteins
  - A gene is a length of DNA that codes for more than 1 polypeptide.
    - The genetic code
      - Triplet Code - A sequence of 3 nucleotide bases code for an amino acid.
      - Degenerate code - All amino acids except methionine have more than 1 code.
      - Some codes indicate a stop e.g. UAC
  - Genome - the entire DNA sequence of an organism.
  - Each gene occupies a specific place (locus) on the chromosomes.
  - Genes code for many polypeptides e.g. haemoglobin, antigens, electron carries and enzymes.
- Transcription
  - 1st stage of protein synthesis
  - Template strand of DNA used (only 1 strand used)
  - 1. A gene to be transcribed unwinds and unzips, dips into nucleolus, hydrogen bonds break
    - 2. RNA nucleotides bind using H-bonds, to their exposed complementary bases on the template strand. Catalysed by RNA polymerase
      - 3. The 2 extra phosphates are released - releases energy for bonding nucleotides.
        4. The mRNA produced is complementary to the nucleotide base sequence on the template strand of DNA - is a copy of the coding strand of DNA.
        5. The mRNA is released from the DNA and passes out of the nucleus, through a nuclear pore, to a ribosome.
Genes code for many polypeptides e.g. haemoglobin, antigens, electron carries and enzymes.

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