DO NOW: How many chromosomes are in each of the four cells below?

Binary Fission in Prokaryotes 1. Chromosome copies 2. Growth 3. Division

Cell Cycle

Rate of Cell Cycle depends on the cell: - Fast: embryo - Fastest: skin, digestive tract - Don’t divide: muscle (heart) and nerve (brain) The Life Cycle of a cell

Interphase - First stage & longest of cell cycle - Nucleus and nucleolus clearly visible - Chromosomes not visible. - Not part of “Mitosis” G 1 = growth and activity S = chromosomes copied G 2 = final preparations for cell division G 0 = do not copy or divide

Cell Division Stage of the cell cycle when the cell is actually dividing. 2 stage process: 1. Mitosis – the nucleus divides and each daughter cell is identical to the parent cell 2. Cytokinesis – cytoplasm divides

The Four phases of Mitosis PMAT

Prophase   chromatin condenses (chromosomes are now visible)   Chromosomes consist of two sister chromatids   nuclear membrane disappears   Centrosomes start to move to opposite ends (poles) of cell   Spindle fibers begin to form   Kinetochore Fibers   Polar Fibers

Metaphase Spindles are fully formed kinetochore fibers move chromosomes to line up at the center (equator) of the cell

Anaphase Sister chromatids separate and move to opposite poles. Each chromatid is now considered an individual chromosome

Telophase 2 nuclear envelopes reform Chromosomes uncoil into chromatin Spindles disappear

Cytokensis cytoplasm is divided in half  ANIMAL PLANT 

Animation of Mitosis

1. Why does the nucleus enlarge during the S phase? 2. If the cell meets all the criteria at each of its checkpoints, it finally enters the M phase. Describe what happens during this final stage of the cell cycle. 3. Do all cells complete the cell cycle or go through it at the same rate?