Unit 2.7 - Genetic Control of Metabolism

• How can wild strains of microorganisms be grouped?

  Selected and cultured.
• How can wild strains be improved?

  Mutagenesis and recombinant DNA technology
• Describe mutagenesis

  Exposure to UV light and other forms of radiation or mutagenic chemicals results in mutations, some of which ,ay produce an improved strain of micro-organism.
• What is recombinant DNA technology?

  The transfer of genes from one species of organism to another enabling the second organism to produce a specific protein.
• What is a vector?

  DNA used to carry foreign genetic material into another cell and both plasmids and artificial chromosomes are used as vectors during recombinant DNA technology.
• Why would artificial chromosomes be better than plasmids?

  More efficient when larger fragments of foreign DNA are required to be inserted.
• What are restriction endonucleases?

  Enzymes which cut open plasmids and specific genes out of chromosomes, leaving sticky ends.
• Describe restriction sites

  Restriction sites contain target sequences of DNA where specific restriction endonucleases cut
• Explain the cutting process

  The complementary sequence in the vector is cut open to alloe the DNA sequence of the required gene to be placed in. Complementary sticky ends are produced when the same endonuclease is used to cut open the plasmid and the gene from the chromosome. Ligase seals the sticky ends of the required DNA fragment to the sticky ends in the vector.
• Describe recombinant vectors.

  Recombinant plasmids and artificial chromosomes contain restriction sites, regulatory sequences, and origin of replication and selectable markers. Regulatory sequences are added that control gene expression.
• What is the origin of replication?

  The origin of replication is a group of genes that allows self-replication of the plasmids/artificial chromosomes.
• What are selectable markers?

  Genes such as antibiotic resistance protect the microorganism from a slective agent (antibiotic) that would normally kill it or prevent it growing. Selectable marker genes present in the vector ensure that only micro-organisms that have taken up the vector grow in the presence of the selective agent.
• Describe the health and safety

  Genes are often introduced that prevent the survival of the microorganism in an external environment
• Why use recombinant yeast cells?

  Plant and animal recombinant DNA expressed in bacteria can be incorrectly folded. Yeast can produce active forms of the protein which are inactive in bacteria.