Physical and chemical mutagens causing mutation.

1. Physical and Chemical
Mutagens
Submitted To ;
Dr. Snober Mir
Head of Department,
Biosciences
Submitted By;
Ameer Abbas & Jasmine Naaz
M.Sc. (Biotechnology)
Semester 2

2. Mutagen
● A mutagen is substance or agent that cause a mutation, or a change in the
sequence or structure of DNA.
● Mutagens cause changes to the DNA that can affect the transcription and
replication of the DNA, which in severe cases can lead to cell death.
● Powerful mutagens may causing chromosomal breakages and
rearrangement of the chromosomes such as translocation, deletion, and
inversion. Such mutagens are called clastogens.

3. Types of Mutagen
❏ Physical Mutagens
❏ Chemical Mutagens

4. Physical Mutagens
● A physical agent that causes mutation referred to as physical mutagens.
● It include electromagnetic radiation, such as gamma rays, X rays, and UV
light, and particle radiation, such as fast and thermal neutrons, beta and
alpha particles.
● It may be of ionizing or non-ionizing in nature.
● Ionizing radiation includes X-rays and gamma rays.
● Non-ionizing radiation includes electromagnetic radiations as visible lights
and in other forms.

5. ❏ Ionizing Radiation
● Ionizing radiation damages the genetic material in reproductive cells and
results in mutation that are transmitted from generation to generation.
● It includes X-ray, gamma rays, alpha- and beta- particles.
● It breaks the covalent bonds including those in DNA.
● The severity of the effects depends upon the dose received.

6. ❏ Non- ionizing Radiation
● Non-ionizing radiation with higher wavelength and lower penetrance that
disturb the hydrogen bonds by introducing thymine dimers in DNA chains.
● UV (254-260 nm) causes purines and pyrimidines to form abnormal dimer
bonds and bulges in the DNA strands.

7. Chemical Mutagens
● The chemical substances or compounds that alters the DNA sequences and
causes mutation are referred to as chemical mutagen.
It consists of following classes of mutagens as -
● Base Analogs
● Base Modifying Agents
● Intercalating Agents

8. ❏ Base Analogs
● Base analogs are the molecules that can substitute for normal bases in
sequences.
● Usually causes mis-pairing.
● e.g., 5-bromouracil, 2-aminopurine, AZT(azidothymidine)

9. ● 5-Bromouracil in its normal state behaves as an thymine and pairs with
adenine molecule. When it replaces T probably get a mutation due to
tautomerization during replication and results from AT to GC.

10. ❏ Base Modifying Agents
● Deaminating Agents are nitrous acid (HNO2
) that removes amine group
from bases-

11. ● Alkylating agents like ethylmethane-sulfonate transfers an alkyl group.

12. ● Hydroxylating agents like hydroxylamine adds a hydroxyl group to the base.

13. ❏ Intercalating Agents
● The substances which can insert themselves into the DNA structure
between bases and causes mutation referred to as intercalating agent.
● e.g., pro-flavin, ethidium bromide, acridine orange

14. ● Intercalating agents causes mutation by addition or deletion of base-pairs.

15. Thank You