Glossary 
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Mesenchymal stem cells: Cells from the immature embryonic con- 
nective tissue. A number of cell types come from mesenchymal stem 
cells, including chondrocytes, which produce cartilage. (NIH) 
Mesoderm: Middle layer of a group of cells derived from the inner 
cell mass of the blastocyst; it gives rise to.bone, muscle, and connec- 
tive tissue. (NIH) 
Metachromatic leukodystrophy: A heritable metabolic disorder, 
usually of infancy, characterized by myelin loss and other abnormali- 
ties of the white matter of the nervous system, leading to progressive 
paralysis and mental retardation or dementia. (SMD) 
Mitochondria: Small, energy-producing organelles inside cells. 
Mitochondrial DNA: Genetic material inside the mitochondria. Es- 
sentially all the mitochondria of an individual come from the cyto- 
plasm of the egg, so all mitochondrial DNA is inherited through the 
maternal line. 
Mitochondrial proteins: Proteins that are part of the mitochondria. 
Mitosis: Cell division, resulting in two cells that each have the dip- 
loid number of chromosomes and are just like the original cell. 
Morphology: Configuration or structure, shape. 
Mutagenicity: Tendency to promote mutations, that is, genetic al- 
terations. 
Multipotent: As applied to stem cells, the ability to differentiate into 
at least two, more differentiated descendant cells. 
Multipotent adult progenitor cells (MAPC): Cells isolated from bone 
marrow that can be differentiated into cells with characteristics of 
cartilage, fat, and bone. 
Mycoplasma: A general category of microorganisms that shares 
some characteristics of bacteria. 
Natural killer cell: A cell type of the immune system that destroys 
tumor cells and cells infected with some types of organisms. 
PRE -PUBLICATION VERSION 
