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A type of embryological study in which the history of individual blastomeres (cells formed during division of the zygote) or meristem cells is traced to their ultimate differentiation into tissues and organs.
The question of how the animal genome can be regulated to produce the various cell types found in the larval and adult organism is a central concern in developmental biology. A possible approach to this problem would involve tracing the structural fates of the descendants of each of a population of progenitor cells, and then trying to determine which gene products are required for particular steps in the process of cell differentiation.
Some of the most promising cell lineage studies are conducted on a nematode worm, Caenorhabditis elegans, which is a small (1 mm or 0.04 in. in length), nearly transparent worm that lives in soil. Adults are either males or hermaphrodites; the hermaphrodites contain 959 somatic nuclei. The origin of each somatic cell can be traced back to a single blastomere, and the clonal history of each cell has been determined. A detailed genetic map for the 80,000-kilobase genome has been worked out. See Cleavage (embryology), Fate maps (embryology)
Cell lineage analysis in plants, as in animals, involves tracing the origin of particular cells in the adult body back to their progenitor cells. The adult body of a typical plant consists primarily of leaves, stems, and roots. Cells arise continuously during plant life from specialized dividing cell populations called meristems. A shoot apical meristem produces the leaves and stem, and a root apical meristem produces root tissue. The shoot apical meristem will also produce specialized structures, such as cones, flowers, and thorns. Because plant cells do not move during development, and in many cases the plane of cell division is constant, lines of cells, called cell files, all derive from a single meristem cell at the base of the file.