Dictionary

mitotic Pertaining to mitosis.

mitosis The ordinary division of a body cell (a somatic cell) to form two daughter cells, each with the same chromosome complement as the parent cell.

mitochondrion Singular of mitochondria.

mitochondrial myopathy A form of mitochondrial disease that leads to progressive muscle weakness. More than 25 types of enzyme abnormalities have been defined that fall into this category. They result in a disease of cell metabolism and are defined via a biopsy of muscle tissue that shows ragged red fibers under microscopic examination. See also…

mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes See MELAS syndrome.

mitochondrial DNA The DNA of the mitochondria. Abbreviated mtDNA. There are 2 to 10 copies of the mtDNA genome in each mitochondrion. The mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes mtDNA molecule is double-stranded and circular. It is very small compared to the chromosomes in the nucleus, and so it contains only a limited number…

mitochondrial disease A mutation in the mitochondrial chromosome that is responsible for a disease. Known mitochondrial diseases include the eye disease Leber hereditary optic atrophy; myoclonus epilepsy with ragged red fibers (MERRF); and mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes syndrome (MELAS syndrome).

mitochondrial Referring to mitochondria.

mitochondria Structures located in the cell’s cytoplasm outside the nucleus. Mitochondria are responsible for energy production. Each consists of two sets of membranes: a smooth, continuous outer coat and an inner membrane arranged in tubules or in folds that form plate-like double membranes (cristae). The mitochrondria are the principal energy source of the cell. They…

mite-borne typhus See typhus, scrub.

missense mutation A genetic change that results in the substitution of one amino acid in protein for another. A missense mutation is responsible for sickle hemoglobin, the molecular basis of sickle cell trait and sickle cell anemia.

miscarriages, multiple More than one miscarriage for a woman. In multiple miscarriages, there is about a 5 percent chance that one member of the couple is carrying a chromosome translocation that is responsible for the miscarriages. Other causes of multiple miscarriage include Rh incompatibility, exposure to toxic substances that harmed the embryo, and physical problems…