1.2 The Cell Cycle & Mitosis “You Complete Me” A process where one parent cell gives rise to two daughter cells- exact 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: • Interphase:growth and preparation • Mitosis: the process of duplicating the nucleus, (PMAT) • 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.
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: • Prophase, P • Metaphase, M • Anaphase, A • 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.
This cycle this repeats itself again!
Body Cell Chromosome Numbers During Mitosis Parent Cell 2 Identical Daughter Cells
Can you identify these stages? A B D C Answers: A. Telophase B. Prophase C. Cytokinesis D. Metaphase
Mitosis - Video • http://www.bing.com/videos/search?q=mitosis&FORM=HDRSC3#view=detail&mid=4EB754393EBFF004C8EC4EB754393EBFF004C8EC
Homework • Read Pages 2. Complete: Pg