(mū-tā'shŏn )

[L. mutatio, a change]

1. Change, transformation, or an instance of change.
2. A permanent variation in genetic structure with offspring differing from parents in a characteristic. It is differentiated by gradual variation through many generations.
3. A change in a gene potentially capable of being transmitted to offspring.

conservative m.A mutation in DNA or RNA that results in the replacement of an amino acid with one that has a similar structure, e.g., glycine replaced by alanine.

driver m.A mutation in a cell that either stimulates the cell to become cancerous or makes an established cancer cell thrive.

engineered m.Targeted mutation.

escape m.A mutation made by a microorganism of its genotype and phenotype to defend itself from host immune responses. Organisms with a high rate of mutations, e.g., HIV, rely on mutational escape as one mechanism to avoid destruction by host cells. SYN: mutational escape.

factor V Leiden m.An autosomal dominant mutation in coagulation factor V that is found in about 5% of all European-Americans. It produces a hypercoagulable state as a result of inherited resistance to activated protein C. Clinically, it is found in many patients with deep venous thrombosis.

founder m.An altered gene that proliferates in a kinship or community from a single identifiable ancestor.

frameshift m.The deletion or insertion of one or two DNA nucleotides that alters the transcription of each subsequent triplet.

gain-of-function m.A mutation in DNA that results in the synthesis of a protein with a new or different function. Gain-of-function mutations are typically dominant.

germline m.A mutation in the genetic content of a sperm or egg. Germline mutations are heritable.

inactivating m.Loss-of-function mutation.

induced m.A mutation resulting from exposure to x-rays, radioactive substances, and certain drugs and chemicals.

JAK2 m.A mutation found on chromosome 9 in myeloproliferative disorders such as polycythemia vera.

loss-of-function m.A mutation in DNA that results in the decreased production of a protein or a protein with impaired function. Loss-of-function mutations are usually recessive. SYN: inactivating mutation .

missense m.A substitution of a single DNA nucleotide for another. This results in the transcription of a different amino acid than is normally found in the protein coded by the gene. Missense mutations are found in diseases such as sickle cell anemia. Red blood cell sickling is caused by the replacement of the amino acid glutamic acid by valine in the sixth position of the beta hemoglobin chain.

natural m.A mutation occurring without artificial external intervention. Natural mutation is thought to be a primary factor in evolutionary change.

nonconservative m. A mutation in DNA that results in the replacement of an amino acid with one that is not biochemically similar, e.g., serine replaced by proline.

nonsense m.A mutation in a single DNA nucleotide that creates a stop codon (TGA, TAA, TAG) that results in the premature termination of protein synthesis.

null m.1A mutation in DNA or RNA that does not result in any change in the protein product or content of a cell.2A mutation in a nucleotide that results in the complete failure of protein synthesis by a cell.

passenger m.A mutation in a cancer cell that does not affect the ability of the cell to progress or reproduce.

point m.A mutation in only one nucleotide in the DNA sequence of a gene. Frame-shift, conservative, nonconservative, missense, nonsense, and silent mutations are examples of point mutations.

regulatory m.A mutation in DNA or RNA that alters the expression of other genes by a cell.

silent m.A mutation in a single nucleotide that does not change the amino acid sequence of a protein, e.g., in DNA, the codons AAA and AAG both designate the amino acid phenylalanine.

somatic m.A mutation occurring in any cell of the body other than a sex cell. These mutations are postzygotic and therefore not heritable.

targeted m.A mutation introduced artificially into a nucleic acid sequence, e.g., to remove an aberrant or unhealthy gene from the DNA of an embryo. SYN: engineered mutation .

transparent m.A single nucleotide substitution that encodes for the same amino acid found in the unsubstituted gene and therefore does not alter the encoded protein.