CB10 Molecular Genetics & Disease

Question 1

Explain the molecular basis of mutagenesis

Answer 1

Mutation is any change in DNA; not all mutations are bad
Mutations in DNA repair genes leads to accelerated mutation rate (associated with cancer)
DNA sequence can be changed by:
- copying errors introduced by DNA polymerase during replication
- environmental agents such as chemical mutagens/radiation

Question 2

Explain the molecular basis of carcinogenesis

Answer 2

Carcinogens are agents that cause cancer
e.g. Chemical, radiation

All carcinogens cause DNA damage

Question 3

Define mutation & explain the different types of mutations

Answer 3

Mutation is any change in the DNA

Point mutation
(Transition-purine to purine; transgression - purine to pyrimidine)

Deletion, insertion, rearrangement of chromosomes
(Structural changes)

Question 4

Know the main categories of mutagen & the types of mutation they cause

Answer 4

• DNA polymerase (point mutation)
• chemicals (point mutation/structural mutation)
• Spontaneous decay (structural mutation)
• oxidative damage (structural mutation)
• energy (structural mutation)
e.g. UV light, radiation

Question 5

Understand the role of mutagenesis in cancer development & progression

Answer 5

• All carcinogens cause DNA damage
• Cancer is associated with high mutation rate
• Mutations in mutation repair genes
• failure to repair mutations in repair genes results in more mutations
• mutations in the telomerase gene results in inappropriate expression of telomerase (immortalises cell)

Question 6

Explain how antibiotics can be targeted to pathogen specific processes

Answer 6

Antibiotics target functions that are important to the pathogen & not the host

1. Inhibition of protein synthesis
2. Inhibition of cell wall synthesis/maintenance
3. Inhibition of DNA replication

Question 7

Explain the ways organisms can become resistant to antibiotics

Answer 7

• Enzymatic breakdown of the antibiotic
• transporters that cause efflux of antibiotic from cell
• metabolic bypass of inhibited reaction
• overproduction of antibiotic target
• reduced uptake into cell
• modification of antibiotic so it does not bind to target

Question 8

Understand the nature of plasmids & their role in antibiotic resistance

Answer 8

• Plasmids are small circular DNA molecules that exist in bacterial cells
• contain an origin of replication plus coding sequences
• coding sequences can be for detoxifying enzymes
• horizontal gene transfer
• carrying a plasmid encoding an antibiotic resistance gene gives the bacterium a growth advantage over other cells