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