The cell cycle, or cell-division cycle, is the series of events that take place in a cell leading to its division and duplication of its DNA (DNA replication) to produce two identical daughter cells. Cells spend most of their time (approximately 90%) in interphase. Interphase is broken into 3 phases, G1 phase -> S phase -> G2 phase. During each one these phases, the cell is doing something different to get ready for division. In G1 phase, the cell is growing; S phase the DNA is replicating (doubling); G2 phase the cell is preparing for mitosis.
Mitosis
During mitosis, the chromosomes (DNA), which have already duplicated, condense and attach to spindle fibers that pull one copy of each chromosome to opposite sides of the cell. The result is two genetically identical daughter nuclei.
The phases of mitosis are: Prophase - chromosomes are condensing and pairing. Metaphase - chromosomes are lining up in the middle Anaphase - chromosomes are now pulled apart by spindle fibers, to opposite sides of the cell. Telophase - Chromosomes are now on opposite sides and both sides have a nucleus. Two nuclei in this one cell.
(Remember PMAT to help remember the correct order.)
After mitosis is preformed the last step of the cell cycle is cytokinesis. In cytokinesis the cytoplasm splits, so we end up with 2 cells. Each of these cells are now back in interphase to start the cycle over again.
Practice Problems 1. List the phases of mitosis in order.
2. Which part of the cell cycle takes the longest amount of time?
3. What is happening when the cell is in the G1 phase? S phase? G2 phase?
4. Which stage of mitosis is the cell in, when all of the chromosomes are lined up in the middle?
5. Which stage of mitosis is the cell in, when the chromosomes are on opposite sides of the cell in their own nucleus?
6. What are the steps of the cell cycle in order?
7. The process where the cytoplasm divides is called ___________.