Dictionary

monocyte A white blood cell that has a single nucleus and can take in (ingest) foreign material.

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…

mitochondrial Referring to mitochondria.

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

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…

mitochondrion Singular of mitochondria.

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.

mitotic Pertaining to mitosis.

mitotic nondisjunction The failure in mitosis for the two members of a chromosome pair to separate (to disjoin) normally so that both chromosomes go to one daughter cell while none go to the other daughter cell. See also mitosis.

mitral insufficiency A malfunction of the mitral valve that permits the backflow of blood (regurgitation) from the left ventricle into the left atrium. Most mitral insufficiency is mild and requires no treatment. When severe, however, treatment with medications and sometimes surgery is necessary.