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NCI Dictionary of Genetics Terms

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11 results found for: M



  • microsatellite  listen  (MY-kroh-SA-teh-lite)
    Repetitive segments of DNA scattered throughout the genome in noncoding regions between genes or within genes (introns). They are often used as markers for linkage analysis because of their naturally occurring high variability in repeat number between individuals. These regions are inherently genetically unstable and susceptible to mutations.

  • microsatellite instability  listen  (MY-kroh-SA-teh-lite in-stuh-BIH-lih-tee)
    A characteristic of cells that contain an abnormality in DNA mismatch repair (see microsatellite). For example, the presence of MSI in colorectal tumor tissue may be used as a marker for germline mutations in one of the DNA mismatch repair genes associated with HNPCC. MSI can also occur sporadically, and in these cases is related to gene hypermethylation. This is an issue in the differential diagnosis of HNPCC. Also called MSI.

  • missense mutation  listen  (MIS-sens myoo-TAY-shun)
    A single base pair substitution that alters the genetic code in a way that produces an amino acid that is different from the usual amino acid at that position. Some missense mutations will alter the function of the protein.

  • MLPA 
    A laboratory method commonly used for the detection of unusual copy number changes (insertions or deletions) of genomic sequences. Also called multiplex ligation-dependent probe amplification.

  • mode of inheritance  listen  (… in-HAYR-ih-tunts)
    The manner in which a genetic trait or disorder is passed from one generation to the next. Autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive, multifactorial, and mitochondrial inheritance are examples. Each mode of inheritance results in a characteristic pattern of affected and unaffected family members.

  • mosaicism  listen  (moh-ZAY-ih-SIH-zum)
    The occurrence of 2 or more cell lines with different genetic or chromosomal make-up, within a single individual or tissue.

  • MSI 
    A characteristic of cells that contain an abnormality in DNA mismatch repair (see microsatellite). For example, the presence of MSI in colorectal tumor tissue may be used as a marker for germline mutations in one of the DNA mismatch repair genes associated with HNPCC. MSI can also occur sporadically, and in these cases is related to gene hypermethylation. This is an issue in the differential diagnosis of HNPCC. Also called microsatellite instability.

  • multiplex genomic test  listen  (MUL-tee-plex jeh-NOH-mik test)
    A method for detecting multiple genetic alterations (i.e., gene mutations or single nucleotide polymorphisms in a single gene or across the genome) simultaneously.

  • multiplex ligation-dependent probe amplification  listen  (MUL-tee-plex ly-GAY-shun-deh-PEN-dent probe AM-plih-fih-KAY-shun)
    A laboratory method commonly used for the detection of unusual copy number changes (insertions or deletions) of genomic sequences. Also called MLPA.

  • mutation  listen  (myoo-TAY-shun)
    A change in the usual DNA sequence at a particular gene locus. Mutations (including polymorphisms) can be harmful, beneficial, or neutral in their effect on cell function.

  • mutation analysis  listen  (myoo-TAY-shun uh-NA-lih-sis)
    Germline genetic testing method targeted to detect a specific mutation (such as a deleterious MSH2 mutation previously identified in a family), panel of mutations (such as the 3 BRCA mutations comprising the founder mutation panel for individuals of Ashkenazi Jewish ancestry) or type of mutation (such as a large deletions or insertions in the BRCA1 gene). This type of testing is distinct from complete gene sequencing or mutation scanning. The latter are designed to detect most mutations in the region being tested. Current usage also applies this term to any genetic test.