mutation
noun
mu·ta·tion
myü-ˈtā-shən 
1
: a significant and basic alteration : change
2
: umlaut
3
a
: a relatively permanent change in hereditary material that involves either a change in chromosome structure or number (as in translocation, deletion, duplication, or polyploidy) or a change in the nucleotide sequence of a gene's codons (as in frameshift or missense errors) and that occurs either in germ cells or in somatic cells but with only those in germ cells being capable of perpetuation by sexual reproduction
Mutations known to cause disease have been identified in approximately 1000 genes.—
Alan E. Guttmacher and Francis S. Collins
Alan E. Guttmacher and Francis S. Collins
also
: the process of producing a mutation
Microorganisms have been used extensively to study mutation … —George A. Wistreich et al.
George A. Wistreich et al.
b
: an individual, strain, or trait resulting from mutation
The worst E. coli bacterium, E. coli 0157:H, a mutation discovered in 1982 that has at least sixty-two subtypes, causes hemorrhagic colitis …—Wayne Biddle
Wayne Biddle
mutationally
adverb
Examples of mutation in a Sentence
The cat's short tail is the result of mutation.
The condition is caused by a genetic mutation.
The building is a mutation of the original design.
Recent Examples on the Web
Pitt-Hopkins and precision gene therapy Pitt-Hopkins syndrome is a rare genetic disorder caused by a mutation in the TCF4 gene, which controls proteins that dictate brain and nervous system development.
—Noah Lyons, San Diego Union-Tribune, 1 Jan. 2026
In 2025, researchers demonstrated that gene therapy could restore hearing in people born with a specific form of hereditary deafness caused by mutations in the OTOF gene.
—Kaif Shaikh, Interesting Engineering, 1 Jan. 2026
One of those, H3N2, has been present for decades, according to the CDC and the Gavi Vaccine Alliance, but its most recent mutation is different enough that the vaccine made to target H3N2 for the 2025-2026 season is not as effective against it.
—Jennifer Borresen, USA Today, 31 Dec. 2025
Among new approvals, for instance, was one for the combination of Rybrevant and Lazcluze, from Johnson & Johnson, which was shown to extend the time before tumors grow significantly in non-small cell lung cancer caused by a mutation in the gene EGFR.
—Matthew Herper, STAT, 31 Dec. 2025
See All Example Sentences for mutation
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Noah Lyons, San Diego Union-Tribune, 1 Jan. 2026
In 2025, researchers demonstrated that gene therapy could restore hearing in people born with a specific form of hereditary deafness caused by mutations in the OTOF gene.
—Kaif Shaikh, Interesting Engineering, 1 Jan. 2026
One of those, H3N2, has been present for decades, according to the CDC and the Gavi Vaccine Alliance, but its most recent mutation is different enough that the vaccine made to target H3N2 for the 2025-2026 season is not as effective against it.
—Jennifer Borresen, USA Today, 31 Dec. 2025
Among new approvals, for instance, was one for the combination of Rybrevant and Lazcluze, from Johnson & Johnson, which was shown to extend the time before tumors grow significantly in non-small cell lung cancer caused by a mutation in the gene EGFR.
—Matthew Herper, STAT, 31 Dec. 2025
See All Example Sentences for mutation
Cite this Entry
“Mutation.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mutation. Accessed 2 Jan. 2026.
Copy CitationKids Definition
mutation
noun
mu·ta·tion
myü-ˈtā-shən
1
: a basic and important change
2
a
: a permanent change in hereditary material involving either a change in the position of the genes on the chromosomes or a basic change in the chemical structure of a gene
also
: the process of producing a mutation
b
: an individual, strain, or trait resulting from mutation
Medical Definition
mutation
noun
mu·ta·tion
myü-ˈtā-shən
1
: a relatively permanent change in hereditary material that involves either a change in chromosome structure or number (as in translocation, deletion, duplication, or polyploidy) or a change in the nucleotide sequence of a gene's codons (as in frameshift or missense errors) and occurs either in germ cells or in somatic cells but with only those in germ cells being capable of perpetuation by sexual reproduction
also
: the process of producing a mutation
2
: an individual, strain, or trait resulting from mutation
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