What causes the mutations?

Question 1

Spontaneous Mutations

Answer 1

• Definition: Occur naturally without external influence.
• Mechanism:
  
  • Errors during DNA replication.
  • DNA polymerase sometimes fails to correct base-pairing errors, leading to point mutations.

Question 2

Induced Mutations

Answer 2

• Definition: Caused by external environmental factors.

Question 3

Induced Mutations (Types of Mutagens):

b. Electromagnetic Radiation

Answer 3

• Low-energy radiation (e.g., UV light):
  
  • Causes adjacent nucleotides to bond, forming thymine dimers.
  • This creates a kink in the DNA, disrupting transcription and translation.
  • High-energy radiation (e.g., X-rays, gamma rays):
    
    • Strips electrons from molecules, causing DNA damage.
    • Leads to deletions or rearrangements of large DNA segments or entire chromosomes.

Question 4

Induced Mutations (Types of Mutagens):

a. Chemical Mutagens

Answer 4

a. Chemical Mutagens
- Enter the nucleus and directly alter the DNA.
- Examples:
- Chemicals that substitute incorrect bases (e.g., nitrous acid).
- Agents that cause insertions or deletions (e.g., intercalating agents like ethidium bromide).