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Topic 6: Reproduction 6-1: Mitosis & Asexual Reproduction.

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Presentation on theme: "Topic 6: Reproduction 6-1: Mitosis & Asexual Reproduction."— Presentation transcript:

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2 Topic 6: Reproduction 6-1: Mitosis & Asexual Reproduction

3  In cell division, the chromosomes are equally divided into two new cells  Each new cell is identical to the parent cell  The division of the chromosomes is called mitosis  After mitosis, the cytoplasm of the cell divides in the process of cytokinesis Cell Division

4 Mitosis (mitotic cell division): produces identical cells; a clone to the parent cell Multicellular Organisms (many cells) Regeneration of Cells/Body Parts Lost; hydra, flatworm, starfish Growth, Development, Replacement & Repair of Cells; large animals, humans Unicellular Organisms (single- celled) Asexual Reproduction: produces a genetically identical offspring; amoeba, bacteria Why Do Cells Divide?

5 Mitosis (mitotic cell division): produces identical cells; a clone to the parent cell Multicellular Organisms (many cells) Growth, Development, Replacement & Repair of Cells; large animals, humans Unicellular Organisms (single-celled) Asexual Reproduction: produces a genetically identical offspring; amoeba, bacteria Why Do Cells Divide? Regeneration of Cells/Body Parts Lost; hydra, flatworm, starfish

6  One parent  Produces a genetically identical offspring (clone)  Offspring (daughter cell) has the exact same DNA as the parent cell  Number of chromosome is identical (diploid, 2n)  Diploid: cells with sets of chromosomes in pairs of 2  Advantage: many offspring may be produced quickly  Disadvantage: there is NO VARIATION Asexual Reproduction

7 Single-celled organisms divide asexually as a means of reproduction Human cells perform asexual reproduction to grow & repair. Remember…

8  Mitosis: chromosomes duplicate, form 2 nuclei, and split into 2 identical cells  Cells divide in order to multiply Division = Multiplication

9 Overview of Mitosis interphaseprophase metaphaseanaphasetelophase cytokinesis I mmediately P lease M ake A nother T wo C ells

10 Mitosis in Real Time

11 Interphase  Interphase is the part of the cell cycle when the cell grows and duplicates its chromosomes  Occurs just before mitosis begins.

12 Prophase  The first stage of mitosis  The chromosomes shorten and thicken  The centrioles move to opposite ends of the cell  The nuclear membrane breaks down and the nucleus disappears Centrioles Replicated chromosomes Nuclear membrane

13 Metaphase  The second stage of mitosis  Spindle fibers are made by the centrioles  The chromosomes line up across the middle of the cell  The spindle fibers attach to the centromeres of the chromosomes  Tip: Remember Middle / Metaphase Spindle

14 Anaphase  The third stage of mitosis  The centromeres that connect the chromatids divide (move apart)  The spindle fibers move the chromatids to opposite ends of the cell  Tip: Remember Anaphase / Apart

15 Telophase  The last stage of mitosis  Each end of the cell now has an identical set of chromosomes  Nuclear membranes form around each set of chromosomes  Cytokinesis can now occur Nuclear membrane

16 Cytokinesis  In animal cells, the cell membrane pinches in the middle to form a cleavage furrow  When the pinching in is complete, two identical daughter cells are formed Cleavage furrow

17  In plant cells, a cell plate is used instead of a cleavage furrow  The cell plate grows in the middle of the cell and will become a new cell wall Cytokinesis

18 Budding in Hydra & Yeast

19 Regeneration

20 Binary Fission

21  Since asexually produced offspring are clones of the parent cell, there is no variation within the population.  If there is a change to the environment, they may not be able to adapt to changes or survive.  However, if the parent has a trait with high adaptive value (genes that allow it to survive), it will be passed on to the next generation.  Ex: resistance to antibiotics, pesticides, etc. Disadvantage: No Variation

22 Cancer  Cancer cells show uncontrolled cell division  They grow even when there is no more room and forms a mass called a tumor  Tumors steal energy and nutrients from normal tissues  Benign tumors stay in their original location and do not spread

23 Cancer  Malignant tumors spread throughout the body when cancer cells break off from the tumor and travel in the blood  The spread of cancer is called metastasis  All body tissues can be affected with cancer  Cancer is caused by mutations in DNA  Substances that cause these mutations that lead to cancer are called carcinogens

24 Mitosis in whitefish embryo

25 Mitosis in plant cell

26 onion root tip

27 Mitosis Video


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