Mutation Causes

Key Concepts: Causes of Mutations

What Causes Mutations?

Mutations can happen due to:

  1. Spontaneous changes during DNA replication or transcription.

  2. Environmental factors called mutagens.



Types of Mutagens

Mutagens are environmental agents that cause DNA mutations.

Type of Mutagen

Description

Examples

Radiation

High-energy waves break DNA strands

UV rays, X-rays, nuclear radiation

Chemicals

Chemicals alter or damage DNA bases

Tobacco smoke, pesticides, benzene

Infectious Agents

Some viruses insert their DNA into host cells

HPV (causes cervical cancer), Helicobacter pylori (linked to stomach cancer)



Spontaneous Mutations

These occur without external mutagens due to natural errors in DNA processes.

Mutation Type

Description

Tautomerism

A base temporarily changes its structure due to hydrogen movement, leading to mispairing.

Depurination

Loss of a purine base (adenine or guanine) from the DNA strand.

Deamination

Loss of an amino group from a base, often changing cytosine (C) into uracil (U).

Transition

A purine is replaced with another purine (A ↔ G) or a pyrimidine with another pyrimidine (C ↔ T).

Transversion

A purine (A or G) is swapped with a pyrimidine (C or T), or vice versa.



Chernobyl Disaster: A Case Study in Mutation

  • The Chernobyl nuclear disaster (1986) released radiation, a powerful mutagen.

  • Radiation exposure caused increased cancer rates (up to 1.4 million excess cases).

  • Despite radiation, the Chernobyl Exclusion Zone has become a wildlife sanctuary, showing how some species adapt to environmental changes.



Check Your Understanding

1. Define Mutation and Mutagen.

  • A mutation is a change in DNA sequence.

  • A mutagen is an environmental factor that causes mutations.

2. List Three Examples of Mutagens.

  • Radiation: UV rays, X-rays

  • Chemicals: Cigarette smoke, pesticides

  • Infectious Agents: HPV, Helicobacter pylori

3. Distinguish Between a Transition and a Transversion.

  • Transition: Swaps a purine for a purine (A ↔ G) or a pyrimidine for a pyrimidine (C ↔ T).

  • Transversion: Swaps a purine for a pyrimidine (A/G ↔ C/T) or vice versa.