Chemical Mutagens and Agents

Andria Emerson, Katy Metzler
  • Author
    Andria Emerson

    Andria Emerson has taught high school science for over 17 years. She has a M.S from Grand Canyon University in Educational Leadership and Administration, M.S from Grand Canyon University in Adult Education and Distance Learning, and a B.S from the University of Arizona in Molecular and Cellular Biology.

  • Instructor
    Katy Metzler

    Katy teaches biology at the college level and did her Ph.D. work on infectious diseases and immunology.

Learn examples of chemical mutagens and how they damage associated molecular patterns in DNA. Find out the relationship between carcinogens and mutations. Updated: 03/11/2022

Table of Contents



Deoxyribonucleic acid (DNA) contains the genetic information that is passed down from generation to generation. Although the methods for how genetic information is passed vary from species to species, all instructions to make an organism are contained in this genetic blueprint.

Mutations are changes in DNA sequences that lead to changes in genetic traits. Mutations can be harmful causing birth defects such as trisomy 21, heart defects, abnormal limbs, cancer, and many different diseases. Not all mutagenic effects are harmful. In fact, mutations are the source of all biodiversity on the plant. Mutations are the reason humans look different. They are the reason there are so many variations of dogs. Variation in a species is necessary especially in nature to ensure the survival of the species.

Although there are different causes for mutations, the two main mutagenic agents are irradiation and chemical mutagens. These are chemical or physical agents able to change the DNA sequence in a harmful way.

  • Irradiation occurs when objects are exposed to radiation.
  • Chemical mutagens are naturally occurring or synthetic chemicals that can cause mutation or damage associated molecular patterns.

Mutagens vs. Carcinogens

What is the relationship between carcinogens and mutations? Carcinogens are biological, physical, or chemical agents that increase the risk for cancer. Are all mutagens carcinogens? Many mutagens are carcinogens, but not all.

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  • 0:01 Mutations
  • 1:11 Base Analogs
  • 4:11 Base-Modifying Agents
  • 6:21 Intercalating Agents
  • 7:38 Lesson Summary
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Base Analog Mutagens

The building blocks of DNA are nucleotides. Each nucleotide is identical except the base attached to the 5 carbon sugar. These bases link together by hydrogen bonds forming a double helix of two DNA strands. The word base refers to the nitrogenous base in the nucleotide. All living organisms have the same four bases that pair together making up their DNA.

A= Adenine pairs with T= Thymine

C= Cytosine pairs with G= Guanine

DNA is a double helix made of two strands.

mutagenic agents

The variation in the sequence of these bases is what makes organisms unique. The image here shows how bases code for specific amino acids. For example, GCA codes for the amino acid Ala (alanine) and AGA codes for the amino acid Arg (arginine). The sequence of amino acids forms proteins necessary for all living organisms to survive.

DNA is made of four bases: A, T, G, C

mutagenic agents

Some mutagens are analogs of DNA meaning they are very similar to the bases of DNA. Base analogs are mutagens that are incorporated into DNA in place of normal bases causing mutations. If a base analog mutagen is present during DNA replication (copying of DNA), the molecule DNA polymerase, which is responsible for pairing nucleotides, may insert one of the base analogs in the DNA strand rather than the original nucleotide. These decoy nucleotides are put into DNA instead of normal nucleotides and can the shape-shift causing mispairing.

Examples of chemical mutagens that are base analogs include 5-Bromouracil and 2-Aminopurine.

Base analog 5-Bromouracil (or 5BU)

5-Bromouracil (5BU or BrU) is a base analog of thymine and pairs with adenine. Once incorporated into DNA, BrU can cause a T-A base pair to change to a G-C base pair during DNA replication.

Base Analog 2-Aminopurine

2-Aminopurine is a base analog to adenine. This means it resembles adenine. Once incorporated into DNA, 2-Aminopurine can cause A-T base pairs to change to G-C base pairs.

Base Modifying Agents

Base pair modifying agents are chemicals that actually change the chemical structure of certain nucleotides (bases) in DNA causing them to mis-pair. Examples of base modifying agents include nitrous acid, hydroxylamine, and ethyl methanesulfonate.

Nitrous Acid

Nitrous acid is a deaminator meaning it removes an amino group ({eq}NH_{2} {/eq}) from nucleotide bases. This image shows the base cytosine with its associated amino acid group. Nitrous acid is able to convert cytosine into uracil (a base used during RNA transcription). Uracil pairs with adenine (U-T). When this strand of DNA is replicated, the once cytosine pair, which should have been C-G, is now A-T.

Deaminators convert cytosine into uracil by removing an amino acid group.

mutagenic agents


Hydroxylamine adds a hydroxyl group (OH) to cytosine making it resemble thymine. This causes C-G base pairs to turn into T-A base pairs.

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Frequently Asked Questions

How do chemical mutagens cause mutation?

Chemical mutagens cause mutations by changing bases in DNA. These mutagens can cause base pairs to change or insert basepairs causing framsehifts.

What are three types of mutagens?

Mutagens cause changes in the base pairs of DNA. Three different types of mutagens are 5-Bromouracil (5BU or BrU), 2-Aminopurine, and nitrous acid.

What is an example of mutagenic agent?

There are many different types of mutagenic agents. The two main types are irradiation, which occurs when objects are exposed to radiation and chemical mutagens, which are naturally occurring or synthetic chemicals.

What are common chemical mutagens?

Chemical mutagens are naturally occurring or synthetic chemicals that can cause mutation. Examples include base analog mutagens, which appear to look like original bases and base modifying agents which actually change bases.

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