Honors Biology CELL DIVISION & DIFFERENTIATION

 What are some reasons why cells divide?  Replacement  Growth  Regeneration  Too big (more on that later) WHY CELLS DIVIDE

 All cells have the same genes (information)  So how do they become different?  Gene activation (differentiation)  As a cell differentiates, some genes are turned on and some are turned off  Like a computer with all information, but only certain programs are turned on, others are off DIFFERENTIATION

 Undifferentiated cells (their job is to become special cells when needed)  They can be grown continuously in a culture (stem cell line)  They can be induced (using chemicals) to become cells with special functions STEM CELLS

 Embryonic  Obtained from fertilized eggs left over from in vitro fertilization (IVF)  Controversial  Adult  Both children and adults have them in specific areas (niche) to divide and differentiate when needed  Not as programmable as embryonic stem cells TYPES OF STEM CELLS

THE CELL CYCLE