The Cell Cycle and Mitosis• Cell Division in Prokaryotes– Prokaryotes hav one circular chromosome– Binary Fission- the division of a prokaryotic cell
into two offspring cells• DNA is copied, forming two identical chromosomes• Cell grows until it reaches approximately twice the cell’s
original size
• Cell division in Eukaryotes–Cell Cycle –repeating set of events in life of
cell– Interphase- time between cell divisions• G1 phase- cells grow to mature size• S phase- cell’s DNA is copied (synthesized)• G2 phase- Time during which cell prepare fro
cell division–Cell Division:• Mitosis- the nucleus of cell divides• Cytokinesis- division of cell’s cytoplasm
• Cell division in Eukaryotes https://wps.prenhall.com/wps/media/objects/486/498658/CDA8_1/CDA8_1b/CDA8_1b.htm
• Stages of Mitosis– Prophase 1. DNA condenses
into chromosomes2. Centrosomes move
to opposite poles3. Mitotic spindle
starts to form
• Metaphase– Chromosomes move
to center of dividing cell
• Anaphase– Chromatids of each
chromosome separate and move toward opposite poles
• Telophase1. Spindle fibers
disassemble2. Chromosomes return
to a less tightly coiled chromatin state
3. Nuclear envelope forms around each set of chromosomes
4. Nucleolus forms in each of the newly forming cells
• Cytokinesis- division of cytoplasm– In Animal Cells
1. Cytokinesis begins with a pinching inward of the cell; cleavage furrow
2. Cleavage furrow pinches the one cell into two cells
– In Plant Cells1. Vesicles from Golgi
apparatus join together at midline of dividing cell to form Cell Plate
https://wps.prenhall.com/wps/media/objects/486/498658/CDA8_2/CDA8_2a/CDA8_2a.htm
• Control of Cell Division– Control occurs at 3 main checkpoints
1. Cell growth (G1) checkpoint- if cell is healthy and has grown to suitable size during G1 phase, proteins initiate DNA synthesis (S phase)
2. DNA synthesis (G2) checkpoint- DNA repair enzymes check the results of DNA replication. IF ok, then cell proceeds with mitosis
3. Mitosis checkpoint- if cell passes this checkpoint, proteins signal the cell to exit mitosis.
– Cancer, the uncontrolled growth of cells is caused by mutations in the checkpoint proteins