Warm-Up (11/09) On the piece of white paper from the back, answer the following question. Name Date Period Explain the importance of DNA replication.

The Cell Cycle Interphase Growth (G1) Synthesis of DNA (S) Preparation for mitosis (G2)

Two identical “daughter” cells Mitosis Two identical “daughter” cells original cell

Mitosis “2n” “4n” “2n” Two identical “daughter” cells 4 copies of every chromosome “4n” Chromosome: a long, tightly compacted strand of DNA original cell 2 copies of every chromosome “2n”

Mitosis “2n” “4n” “2n” Two identical “daughter” cells 4 copies of every chromosome “4n” Chromosome: a long, tightly compacted strand of DNA original cell 2 copies of every chromosome “2n” When cells specialize to perform a specific function, they often “arrest” or stop dividing.

Share and Discuss Discuss this question with your partner and write or represent it. I will call on three people to share their partners’ answers. What would a graph of DNA levels per cell look like over four generations?

Independent Practice Draw a graph of a cell dividing over four generations and label the growth, synthesis and preparation stages of interphase; mitosis; and cytokinesis Draw a graph of a cell dividing over time with an increased cell cycle rate or decreased cell cycle rate

Share and Discuss Discuss this question with your partner and write or represent it. I will call on three people to share their partners’ answers. What would a cell look like after 3 cycles through the cell cycle if it lost the ability to undergo cytokinesis?

Closure On the piece of white paper from the back, answer the following question: Name Date Period Epithelial skin cells are some of the fastest- dividing cells in the human body, which means that they complete and re-enter the cell cycle more quickly than most other cell types. What do you predict would happen if a person was scratched on the arm, killing approximately 10,000 cells from the surface of that person’s skin? Justify your answer. Scale 1 – 10