genetic control of metabolism

• how can wild strains of microorganism be controlled

  1. Mutagenesis
  2. Recombinant DNA technology
• what is mutagenesis?

  Mutagenesis is exposing micro-organisms to UV light and other forms of radiation or mutagenic chemicals resulting in mutations.

  some mutations may produce an improved strain of micro-organism.

  EG. using radiation or UV to induce mutations
• Recombinant DNA technology

  1. DNA from the donor organism is extracted

  2. A restriction endonuclease enzyme is used to cut a DNA fragment containing the required genes from the donor DNA at a restriction site leaving sticky ends

  3. The same restriction endonuclease enzyme is used to cut the vector at restriction sites leaving complementary sticky ends

  4. DNA ligase is used to seal the DNA fragments into the vector to form recombinant DNA by sealing the complementary sticky ends together

  5. The recombinant plasmids are inserted into host cells lacking plasmids

  6. Transformed host cells which contain the recombinant vectors are selected and cultured

  7. Transformed cells translate / transcribe DNA, producing products which can then be extracted
• restriction endonuclease

  cuts DNA fragments from the DNA

  cuts vector open
• DNA ligase

  seals DNA fragment into vector / plasmid
• what is a vector?

  DNA molecule used to carry foreign genetic info into another cell. both plasmids and artificial chromosomes are used as vectors
• artificial chromosomes are better than plasmids as vectors when

  larger fragments of DNA are required to be inserted
• restriction sites

  contain target sequences of DNA where specific restriction endonucleases cut
• regulatory sequence

  control gene expression
• origin of replication

  allows for self-replication of the plasmid or artificial chromosome.
• selectable markers

  gene ensures that only the micro-organisms that have taken up the vector grow in the presence of the selective agent

  EG. antibiotic resistance genes protect the micro-organism from a selective agent (antibiotic) that would normally kill it or prevent it from growing
• a gene from a eukaryote expressed by a prokaryote

  results in the formation of a polypeptide molecule which is inactive because it is not folded properly or lacks certain post translational modifications which are essential for it to function
• safety measure in recombinant DNA technology

  some genes are inserted to stop the microorganism from surviving in an external environment.