
1) Agent 2) It changes genes 3) Radiation
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https://www.crosswordclues.com/clue/mutagen

A substance that causes physical changes in chromosomes or biochemical changes in genes.
Found on
http://experttoxicologist.com/tcas-glossary.aspx

any agent capable of altering the genetic constitution of a cell by changing the structure of the hereditary material, deoxyribonucleic acid (DNA). ... [2 related articles]
Found on
http://www.britannica.com/eb/a-z/m/144

Anything that causes a mutation (a change in the DNA of a cell). DNA changes caused by mutagens may harm cells and cause certain diseases, such as cancer. Examples of mutagens include radioactive substances, x-rays, ultraviolet radiation, and certain chemicals.
Found on
http://www.cancer.gov/dictionary?expand=M

An agent/substance that is capable of increasing the mutation rate.
Found on
http://www.cat-world.com.au/glossary

A mutagen is an agent that causes a permanent heritable change (i.e., a mutation) into the DNA (deoxyribonucleic acid) of an organism.
Found on
http://www.chem.qmul.ac.uk/iupac/medchem/ix.html

Agent causing mutations.
Found on
http://www.chemicalglossary.net/definition/1107-Mutagen

Anything that can cause a change (or mutation) in the genetic material of a living cell.
Found on
http://www.chemicalglossary.net/definition/1131-Mutagen

Any agent or process that can cause mutations. See Mutation.
Found on
http://www.encyclo.co.uk/local/20095

A substance which if inhaled, ingested or penetrates the skin may produce a risk of hereditable genetic defects ie a permanent change in the amount or structure of the genetic material which results in a change to the characteristic of the daughter cells.
Found on
http://www.encyclo.co.uk/local/20474

<chemistry, oncology> An agent that can cause an increase in the rate of mutation, includes X-rays, ultraviolet irradiation (260 nm) and various chemicals. ... (18 Nov 1997) ...
Found on
http://www.encyclo.co.uk/local/20973

(mu´tә-jәn) an agent that induces genetic mutation.
Found on
http://www.encyclo.co.uk/local/21001

An agent that causes a permanent genetic change in a cell. Does not include changes occurring during
Found on
http://www.encyclo.co.uk/local/22391

An agent that causes a permanent genetic change in a cell other than that which occurs during normal
Found on
http://www.encyclo.co.uk/local/22399

A substance that causes mutations (genetic damage).
Found on
http://www.encyclo.co.uk/local/22412

Agent causing mutations.
Found on
http://www.encyclo.co.uk/visitor-contributions.php

Substance causing genes in an organism to mutate or change.
Found on
http://www.encyclo.co.uk/visitor-contributions.php

Agent that causes biological mutation. Examples include chemicals, radioactive elements and ultraviolet light. See pentachlorophenol.
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http://www.encyclo.co.uk/visitor-contributions.php

A substance or agent that causes genetic mutations, or chemical alteration of the genetic material, DNA
Found on
http://www.i-sis.org.uk/Glossary.php

Mutagen: Something capable of causing a gene-change. Among the known mutagens are radiation, certain chemicals and some viruses.
Found on
http://www.medterms.com/script/main/art.asp?articlekey=4469

An agent capable of modifying the DNA in the genes, causing mutations.
Found on
http://www.roadsafeeurope.com/useful_info/Glossary

anything that can increase the rate of abnormal change in cells, which can lead to cancer
Found on
https://www.encyclo.co.uk/local/20875
noun any agent (physical or environmental) that can induce a genetic mutation or can increase the rate of mutation
Found on
https://www.encyclo.co.uk/local/20974

Any substance that increases the rate of gene mutation. A mutagen may also act as a carcinogen
Found on
https://www.encyclo.co.uk/local/21221

a substance or preparation capable of inducing mutation.
Found on
https://www.infoplease.com/dictionary/mutagen
No exact match found.