Section 8.2 Cell Division

1. Section 8.2Cell Division

2. Cell Division in prokaryotes BINARY FISSION is the division of a prokaryotic cell into 2 offspring cells Binary Fission consist of THREE General Stages: ��� STAGE 1 � The chromosomes, which is attached to the inside of the cell membrane, makes a copy of itself, resulting in 2 identical chromosomes attached to the inside of the inner cell membrane ��� STAGE 2 � the cell continues to grow until it reaches approx. twice its normal size. Then a cell wall begins to form between the two chromosomes ��� STAGE 3 � the cell splits into 2 new cells. Each new cell contains identical chromosomes

3. Cell Division in eukaryotes The trillions of cells that make up your body came from just one original cell called, a fertilized egg (zygote) Each time a cell reproduces, the new cells that are formed contained all the essentials needed to survive and function A cell typically goes through phases during its life, performing life processes before it divides into new cells

4. The phases of the life of a cell are called the Cell Cycle. Cell cycle contains 3 phases: Interphase G1 phase S phase G2 phase Mitosis Prophase Metaphase Anaphasse Telophase cytokinesis

5. Cell cycle Cell cycle is repeating events that make up the life of a cell Cell division is one phase of the cycle. Consists of mitosis and cytokinesis Mitosis is a series of phases in cell division during which the nucleus of a cell divides into 2 nuclei with identical genetic material. Occurs only in eukaryotes

6. Interphase Interphase is the portion of the cell cycle between division The longest phase in the cell cycle. Used to be referred to as the resting phase During interphase, cells carry on all their usual functions, Cells also grow and develop into mature functioning cells while in interphase.

7. Interphase 3 phases G1 Phase � period of normal metabolic cellular activates. The number of organelles and amount of cytoplasm in a cell increase. Offspring cells grow to mature size S Phase � the genetic material (DNA) is duplicated (copied) and the chromosomes of the cell replicate G2 Phase � structure directly involved with mitosis are formed. The cell makes the organelles and substances it needs for cell division. A time which during the cell prepares to divide.

8. Replication is the process of copying genetic material Results in two identical copies of a chromosome called sister chromatids Chromosomes must replicate during interphase so there will be a complete copy of each chromosome in the new cell Because the DNA contained in chromosomes control growth development and function of every cell, each new cell must have an exact copy of the original set of chromosomes

9. Cell division Cell division is the process by which one cell produces two new identical daughter cells Cell division involves 2 steps: mitotic cell division Mitosis (first step). Series of phases in cell division during which the nucleus of a cell divides into two nuclei with identical genetic material Cytokinesis (second step). Cytoplasm of the cell divides into 2 new cells called daughter cells

10. Daughter cell nuclei are identical to the parent cell nucleus in every way. Like their parent cell, some daughter cells will pass through the cell cycle of growth, development and cell division

11. Mitosis Mitosis is the division of the nucleus, which occurs during cell division Four phases of mitosis are called Prophase Metaphase Anaphase telophase

12. Mitosis is the process by which a nucleus gives rise to 2 identical nuclei Interphase prior to mitosis, the period of normal metabolic activity. The chromosomes replicate and cytoplasm increases as the cell prepares to divide Interphase includes G1, S, G2 phases of the cell cycle

13. 4 phases of mitosis Prophase � first stage. Begins with the shortening and tight coiling of DNA into rod-shaped chromosomes that can be seen with a light microscope Two structures called centrosomes appear next to the disappearing nucleus. In animal cells each centrosome contains a pair of small, cylindrical bodies called centrioles. Plant cells lack centrioles

14. Prophase con�t In both animal and plant cells the centrosomes move toward opposite poles of the cell. When separating, spindle fibers made of microtubules radiate from the centrosomes in preparation for mitosis. The array of spindle fibers is called the mitotic spindle, which servers to equally divide the sister chromatids between the 2 offspring cells.

15. Prophase con�t2 types of spindle fibers Kinetochore fibers � attached to the centromere region of each sister chromatids Polar fibers � extend across the dividing cell from centrosome to centrosome

16. Metaphase (phase 2) Chromosomes are moved to the center of the cell (equatorial plane) by the kinetochore fibers attached to the centromeres The two sister chromatids of each chromosome are attached to kinetochore fibers radiating from opposite ends of the cell

17. Anaphase (phase 3) The centromeres of each chromosome are pulled by the kinetochore fibers toward the ends of the cell (opposite poles) The sister chromatids are thus separated from each other. They are now considered to be individual chromosomes

18. Telophase (phase 4) After the chromosomes reach opposite ends of the cell, the spindle fibers disassemble The chromosomes return to less tightly coiled chromatin state New nuclear envelope begins to form around the chromosomes at each end of the cell Cytokinesis begins Process of mitosis is now complete. Cell membrane begins to pinch the cell in two as cytokinesis begins

19. Cytokinesis Area of the cell membrane that pinches in and eventually separates the dividing cell into 2 cells is called the cleavage furrow Pinches into 2 cells through action of microfilaments

20. Cytokinesis Plant cells vesicles formed by the Golgi apparatus fuse at the midline of the dividing cell, forming a membrane-bound cell wall called the cell plate The cell plate separates the cell into two cells Animal and plants the offspring cells area approx. equal in cell. Each offspring receives an identical copy of the original cell�s chromosomes and approx. one-half of the original cell�s cytoplasm and organelles