Nerve growth factor, fibroblast growth factor, etc. See Methods box, p. 215. Suppresors Also discovered a number of suppressors that block cell division. Recently discovered protein, suppresses tumors. But if gene for this protein mutates in certain places, mutant protein no longer functions to stop cell growth.
Cells contain mechanisms to die as well as grow and divide.
Appear normal for several weeks after birth, birth then get tumors. Karyotypes Can count number of chromosome in metaphase cell. Best done by treating cell with colchicine , a drug that blocks formation of spindle fibers. Almost all cells in dividing population wind up in arrested metaphase. Squash these cells to spread out chromosomes, prepare slide by staining, examine.