Also called lymph glands . The tissues and organs, including the bone marrow, spleen, thymus, and lymph nodes, that produce and store cells that fight infection and disease. This system also has channels that carry lymph . Return to alphabet M Macrorestriction map Map depicting the order of and distance between sites at which restriction enzymes cleave chromosomes. An x-ray of the breast.
Mapping See gene mapping, linkage map, physical map.
Marker A gene with a known location on a chromosome and a clear-cut phenotype, used as a point of reference when mapping a new mutant. Mb See megabase. Meiosis The doubling of gametic chromosome number. Meiosis results in four rather than two daughter cells, each with a haploid set of chromosomes. Melanoma Cancer of the cells that produce pigment in the skin.