This document discusses different types of chemical mutagens that can cause mutations in DNA. It describes four main categories of mutagens: 1) base analogs like bromouracil and aminopurine that are incorporated into DNA instead of normal bases, 2) alkylating agents like mustard gas and ethylnitrosourea that add alkyl groups to DNA, 3) intercalating agents like ethidium bromide that insert between DNA bases, and 4) metal ions like nickel and chromium that can directly damage DNA or produce reactive oxygen species. It provides examples of common mutagens for each category and explains their mechanisms of inducing mutations.

1. CHEMICAL MUTAGENIC
AGENTS
Shirin Shahana.N
BSc.Biotechnology
SIAS

2. CHEMICAL MUTAGENS
• A mutagen is any substance or agent that can cause
a mutation, or change in the sequence or structure
of DNA.
• Chemicals are actually dangerous for the entire
world.
• The first mutagenic effect of the nitrogen mustard
was reported by Charlotte Aurebach in 1942.
• Nitrogen mustard is a gas used during Worldwar 1
and 2.

3. 1)BASE ANALOGS
• These are chemicals similar to the bases of DNA
purine and pyrimidines or structurally resemble the
DNA bases.
• Bromouracil and Aminopurine are 2 common base
analogs incorporated into DNA instead of normal
bases, durung the process of replication.
• The 5-bromouracil are artificially synthesized
molecules -a base analog utilized in the genetic
research which is incorporated in DNA in place of
the thymine.

4. • Instead of the methyl group of the thymine,in the
bromouracil contains Bromine group-highly
resemble to the thymine.
• It pairs with the adenine as like the thymine and
produces the mutation.

5. • Mechanism of 5-bromouracil action is quite
interesting.
• During replication, instead of thymine, it generates
guanine which pairs with the cytosine.

6. • Thus, the TA basepair is replaced by GC basepair at
the end of the replication and this happens because
of the tautomeric shift of 5-BU from 'enol' to 'keto'
form.
• The entire mechanism is shown below:-
•

7. Aminopurines
• Another base analogue is amino purine which is
similar to the adenine and can pair with either T or
C, although pairing with C is less frequent.
• It can also cause AT - GC or GC - AT transition during
the replication.

8. 2)ALKYLATING AGENTS
• Ethylnitrosourea, mustard gas and vinyl chloride are
common alkylating agents that add alkyl group to
the DNA and damages it.
• The agents induce base-pairing errors by increasing
ionization and produces gaps in the DNA strand.
• The alkylated purine bases are removed by the
phenomenon called depurination, although
depurination is not mutagenic and can be repaired
by the DNA -repair pathway.

9. Common Alkylating Agents
• Methylhydrazine.
• Temozolomide
• Dacarbazine
• Busulfan
• Iomustin
• "When nitrites are added to smoked meat, it forms
nitrosamine like mutagen that can break DNA or
creates DNA crosslinking.

10. 3)INTERCALATING AGENTS
• EtBr - Ethidium Bromide is an example.
• Other intercalating agents like proflavin, acridine
orange operated by the same mechanism alike the
EtBr.
• The molecules intercalate between the bases of
DNA and disrupt its structure.
• If it is incorporated during the replication, it can
cause frameshift mutation and also blocks
transcription.

11. •Intercalating agents either cause insertion or deletion and
disrupts the DNA structure.

12. 4)METAL IONS
• Nickel, chromium, cobalt, cadmium, arsenic, iron
are some examples.
• The metal ion work by priducing ROS(reactive
oxygen species) hindering the DNA repair pathway,
cause DNA hypermethylation or may directly
damages the DNA.

13. OTHER CHEMICAL MUTAGENS
• ROS, benzene, synthetuc rubber and rubber
plastics, sodium azide, aromatic amines, alkaloids,
deaminating agents and PAH(polycyclic aromatic
hydrocarbons) are other mutagens that create
different mutations.

14. THANK YOU...