mistakes in DNA. Microsatellite instability is where the length of small sequences of DNA differs between tumor cells and normal cells; their appearance is a clue to the presence of abnormal DNA repair.
(synonyms: MSI, replication error phenotype, RER) The presence of a discrepancy between the size of microsatellites in DNA from tumor tissue compared to nontumor tissue from the same person, resulting from mutations in a gene in the DNA mismatch repair pathway (MMR) that would normally correct these errors.
Microsatellite instability is a change that occurs in the DNA of certain cancer cells in which the number of repeats of microsatellites is different than the number of repeats that was in the DNA before the cancer. Mutations in mismatch repair (MMR) genes cause MSI in some colon tumors.
MSI. A change that occurs in the DNA of certain cells (such as tumor cells) in which the number of repeats of microsatellites (short, repeated sequences of DNA) is different than the number of repeats that was in the DNA when it was inherited. The cause of MSI may be a defect in the ability to repair mistakes made when DNA is copied in the cell.
( my-crow- SA-tuh-lite in-stuh- BILL-uh-tee): a type of genetic mutation often linked to hereditary non-polyposis colon cancer (HNPCC). This mutation causes size differences in sections of DNA that are normally the same size in all a person?s cells. Testing for MSI is done on tissue taken from the cancer to find out if this DNA is of different lengths; if it is, HNPCC genetic testing is usually offered. See also hereditary non-polyposis colon cancer, DNA, mutation, genetic counseling.
Microsatellites are repeated sequences of DNA. Although the length of these microsatellites is highly variable from person to person, each individual has microsatellites of a set length. These repeated sequences are common, and normal.
