LIFESCI 2A03 Lecture Notes - Lecture 5: Adult Stem Cell, Asymmetric Cell Division, Progenitor Cell
18 Oct 2013
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Preformationist theory of development semen contains an embryo, a preformed miniature infant, or homunculus, that becomes larger during development: view persisted into the 18th century, problems. No evidence (microscopy at the time not sufficient) Generational problem inside homunculus there are millions of sperm cells with homunculus, inside whith. Sperm is single cell; suggests many tiny cells within sperm forming homunculus there are millions of sperm etc too microscopic. Other theory was that animal emerges gradually from a relatively formless egg. During the 19th century, improvements in microscopy allowed biologists to see that embryos took shape in a series of progressive steps after the fusion of egg and sperm (germline cells) Adult stem ells cells that can divide to create two cells; another stem cell or a cell more differentiate than itself: cells: Terms stem cell and progenitor cell are often used interchangeably; stem cell pluripotent; progenitor cell more differentiated (multipotent, unipotent) C (yellow) = differentiated or specialized cell: processes.
