Class Notes 5: Mitosis and the Cell Cycle A story where two cells are created from one!

I. What is mitosis? Mitosis is a form of cell division in body cells, resulting in two new cells that are exactly the same as the original. Meiosis is another form of cell division that creates sex cells.

II. Major “characters” in the cell cycle A. Chromosomes: Contain DNA: the instructions to make proteins Centromere Nucleosome DNA Sister Chromatids

B. Centrioles: made of microtubules

C. Spindle: forms between the centrioles to pull chromatids apart.

III. Interphase The cell cycle has 3 phases: 1.interphase 2. Mitosis 3. Cytokinesis B. During interphase, the longest phase, the cell grows, produces proteins and DNA replicates (copies).

IV: Mitosis A. : PROPHASE Chromosomes become visible. Nuclear envelope disappears. Spindle forms between centrioles.

B. Phase 2: METAPHASE Chromosomes line up, creating a plate that splits the cell in half. Spindles move to opposite sides of the plate

C. Phase 3: ANAPHASE Chromosomes are split into chromatids at the centromere. Chromatids are pulled into two separate groups towards opposite sides of the cell.

D. Phase 4: TELOPHASE Spindle breaks down. Chromosomes unwind Two nuclear envelopes form, one around each cluster.

V. Cytokinesis: When 1 cell becomes 2 A. Animal Cells: The plasma membrane simply pinches in to create two new cells.

B. Plants: Form a “cell plate” to divide the cytoplasm between the two new forming cells. The plate will later become the new cell wall.

Summary What are the parts of the cell cycle? What are the phases of mitosis?