2.7) Genetic Control of Metabolism

Question 1

• Explain what mutagenesis is and name examples of mutagenic agents.

Answer 1

• ‘Mutagenesis’
  ➞ process of changing a micro-organism’s genetic material using mutagenic agents.
• Exposure to mutagenic agents results in mutations, some of which may produce an improved strain of micro-organisms.
• Radiation:
  ➞ UV rays
  ➞ X-rays
  ➞ Gamma rays
• Chemical:
  ➞ mustard gas
  ➞ tobacco smoke
  ➞ lead oxide

Question 2

• Explain what recombinant DNA technology is and describe the concept and roles of recombinant plasmids/artificial chromosomes as vectors.

Answer 2

• Recombinant DNA technology
  ➞ is technology involved with transferring the genetic material from one organism to another and combining them together.
• Vector
  ➞ is a DNA molecule used to carry foreign genetic information into another cell (such as plasmids and artifical chromosomes).
• Artifical chromosomes
  ➞ are preferable to plasmids as they can carry larger fragments of foreign DNA that are required to be inserted.

Question 3

• Describe the role of the enzyme RESTRICTION ENDONUCLEASE.

Answer 3

• Restriction endonuclease
  ➞ is an enzyme extracted from bacteria, which can recognise and cut specific sequences of DNA into fragments with sticky ends
  ↳ (pieces of DNA that have unpaired nucleotides at the end of them)
• It is important because it allows for specific genes to be cut out of a source chromosome and can also cut bacterial plasmids.
• It is also used to cut open the plasmid and results in complementary sticky ends being produced.

Question 4

• Describe the role of the enzyme LIGASE.

Answer 4

• Ligase
  ➞ is an enzyme that is able to join 2 different fragments of DNA together, with the sticky ends of the DNA fragments being complementary to each other, allowing ligase to bind them together and seal the gene into the plasmid.

Question 5

• What do recombinant plasmids/artifical chromsomes contain and explain their purposes.

Answer 5

1. RESTRICTION SITES
   ➞ (contain target sequences of DNA where specific restriction endonucleases cut)
2. REGULATORY SEQUENCES
   ➞ (control gene expression)
3. ORIGIN of REPLICATION
   ➞ (allows self-replication of the plasmid/artifical chromosome)
4. SELECTABLE MARKERS
   ➞ (such as antibiotic resistant genes, protect the micro-organism from a selective agent [antibiotic] that would normall kill it or prevent it growing)

Question 6

• Explain the purpose and function of RECOMBINANT YEAST CELLS.

Answer 6

• Reocombinant yeast cells
  ➞ can be used as a vector to produce proteins that would normally be found in animals or plants.
• Recombinant yeast cells
  ➞ are used during Recombinant DNA technology as they produce active forms of the protein.
• Bacterial recombinant DNA
  ➞ may produce animal or plant protein chains (polypeptides) that are inactive as the polypeptides are incorrectly folded and may not be modified correctly after protein synthesis.

Question 7

• Describe a safety mechanism applied to micro-organisms during Recombinant DNA technology.

Answer 7

• As a safety mechanism, genes are often introduced that prevent the survival of micro-organisms in an external environment.