Question

How does a mutagen induce mutation? Explain with examples.

Answer 1

Mutagen

A mutagen is a substance or agent that causes alteration in the genetic material (DNA sequence) of an organism. DNA is the genetic material of the organism which is made up of polynucleotide squences (A, T, G and C). Any change in the DNA sequence induces change in the character of the organism.

Types of mutagens

Mutagens are of different types like biological (example, oncogenic virus), chemical (example, nitric oxide) and physical (example, UV radiations).

Biological mutagens

Biological mutagens include viruses that enter host cells, induce mutation and replicate using the cell's machinery. Examples include human papilomaviruses.

Chemical mutagens

Chemical mutagens include chemicals like colchicine that induce polyploidy by inhibiting spindle formation.

Nitrous acid causes oxidative deamination on A, G and C bases which contain amino groups.

Arcidines and proflavins are very powerful mutages. These can intercalate between DNA bases and interfere with DNA replication.

Base analogues cause mispairing and eventually alter DNA sequences in the subsequent daughter strands produced.

Physical mutagens

Physical mutagens include temperature and radiation. Ultraviolet rays, gamma rays and X-rays induce mutation by breaking the bonds in DNA structure.

For example, UV rays cause thymine dimer formation that disturbs DNA double helix and affects DNA replication.