Click here to see the bigger
image!
|
Although each cell contains a full complement of DNA, cells use genes
selectively. Some genes enable cells to make proteins needed for basic
functions; dubbed housekeeping genes, they are active in many types of cells.
Other genes, however, are inactive most of the time. Some genes play a role in
early development of the embryo and are then shut down forever. Many genes
encode proteins that are unique to a particular kind of cell and that give the
cell its character - making a brain cell, say, different from a bone cell. A
normal cell activates just the genes it needs at the moment and actively
suppresses the rest.
|
