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Transcript
1.2 The Cell Cycle & Mitosis “You Complete Me” A process where one parent cell gives rise to two daughter cellsexact replicas of the original cell. The Cell Cycle Importance of cell division: 1. Helps organisms grow. 2. Helps organisms repair. 3. Helps organisms reproduce. Stages of Cell Cycle There are 3 stages to the cell cycle: 1.Interphase: growth and preparation 2.Mitosis: the process of duplicating the nucleus, (PMAT) 3.Cytokinesis: division of cytoplasm and organelles Stage 1: Interphase Onion root tip (on left side), whitefish (on right side) • The longest of all 3 stages of the cell cycle • The cell grows and prepares to divide by duplicating its DNA and organelles so that it can be shared between the 2 new cells. • The DNA strands, chromosomes copy themselves, they are now identical strands of DNA • This now allows for the new cell to have the same genetic information as the parent cell. Chromosomes duplicate Each strand is called a chromatid centromere Stage 2: Mitosis • Mitosis is the stage where the nucleus divides. • TWO copies of the DNA separate to opposite ends of the cell to make TWO new daughter cells. • There are 4 main phases: 1) Prophase, P 2) Metaphase, M 3) Anaphase, A 4) Telophase, T Phase 1 of Mitosis: Prophase Major processes during this phase: • Chromosomes thicken and become more visible bodies, each pair is made up of identical strands. • Nucleolus disappears • Nuclear membrane around the nucleus begins to dissolve. • 2 centrioles move to opposite ends of the cell • Mesh-like spindle fibres form between centioles • Chromosomes begin to attach to spindle fibres. Phase 2 of Mitosis: Metaphase • Chromosomes attached to spindle fibers line up in the middle (the equator) of the cell • Spindle fibers attach to the centromeres of the chromosomes. Phase 3 of Mitosis: Anaphase • The sister chromatids separate and are pulled to opposite poles of the cell. • Each separate chromatid is called a daughter chromosome. • One complete set of chromosomes moves to each end of the cell. Phase 4 of Mitosis: Telophase • Spindle fibres begin to disappear • Daughter chromosomes stretch out, and become thin and invisible again. • A new nuclear membrane begins to form around the nucleus at each end of the cell. • There are now 2 separate nuclei and the cell is ready to split into 2 Stage 3 of Cell Cycle: Cytokinesis • In this last stage of the cell cycle, the cytoplasm and other organelles are distributed to the two ends of the cell. • In an animal cell the cell membrane pinches in called the cleavage furrow. • This separates the dividing cell into 2 new daughter cells. • Each daughter cell has a nucleus with a complete copy of the parents cell’s DNA and its own organelles. cleavage furrow This cycle this repeats itself again! Body Cell Chromosome Numbers During Mitosis 46 46 Parent Cell 46 2 Identical Daughter Cells Answers: A. Telophase B. Prophase C. Cytokinesis D. Metaphase C D B A Can you identify these stages? Mitosis - Video • http://www.bing.com/videos/search?q=mit osis&FORM=HDRSC3#view=detail&mid= 4EB754393EBFF004C8EC4EB754393EB FF004C8EC Homework 1. Read Pages 2. Complete: Pg