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Mitosis and Meiosis. Why do cells need to divide? -For repair -For growth and development -For survival (nutrients – diffusion) -For reproduction -For.

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Presentation on theme: "Mitosis and Meiosis. Why do cells need to divide? -For repair -For growth and development -For survival (nutrients – diffusion) -For reproduction -For."— Presentation transcript:

1 Mitosis and Meiosis

2 Why do cells need to divide? -For repair -For growth and development -For survival (nutrients – diffusion) -For reproduction -For renewal (replace old worn out cells)

3 Cell division and the Cell Cycle The ability of organisms to reproduce their kind is one characteristic that best distinguishes living things from nonliving matter. The continuity of life from one cell to another is based on the reproduction of cells via cell division. This division process occurs as part of the cell cycle - the life of a cell from its origin in the division of a parent cell until its own division into two.

4 Where are all of the genes for different traits and what is the mechanism for passing these genes to the offspring?

5 Cell Division and Genetic Material Cell division requires the distribution of identical genetic material - DNA - to two daughter cells. –What is remarkable, is the exactnesss with which DNA is passed along, without dilution, from one generation to the next. A cell’s genetic information, packaged as DNA, is called its genome. –In prokaryotes (bacteria), the genome is often a single long DNA molecule. –In eukaryotes, the genome consists of several DNA molecules. A human cell must duplicate about 3 meters of DNA and separate the two copies such that each daughter cell ends up with a complete genome.

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7 23 chromosome pairs in a male human (karyotype)

8 Karyotyping -

9 Mitosis Process for duplicating chromosomes and other cellular components Growth and nuclear division This is the mechanism that ensures that a complete set of genetic material is passed to daughter cells Nuclear division Cell cycle

10 Cell Cycle

11 Binary Fission: Cell Division Without Mitosis or Meiosis – occurs in bacteria cells

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13 Cell cycle and mitosis in animal cells

14 Anaphase Prophase Metaphase Telophase Picture adopted from: http://www.micro.utexas.edu/courses/levin/bio304/genetics/celldiv.htmlhttp://www.micro.utexas.edu/courses/levin/bio304/genetics/celldiv.html Real Pictures

15 Anaphase Prophase Metaphase Telophase Picture adopted from: http://www.uoguelph.ca/zoology/devobio/210labs/mitosis1.htmlhttp://www.uoguelph.ca/zoology/devobio/210labs/mitosis1.html Real Pictures Interphase

16 Longest part of the cell cycle Chromosomes are decondensed at this point Chromosomes are replicated and cell growth occurs

17 Prophase Chromosomes condense Chromosomes are two sister chromatids attached at the centromere The centrosome has duplicated

18 Homologous chromosome pairs Sister chromatids Sister chromatids Centromere

19 Metaphase Mitotic spindle between two centrosomes is formed Chromosomes are aligned along the spindle and the nuclear membrane is broken down

20 Anaphase The centromere separates and the sister chromatids are pulled to opposite poles in the cell

21 Telophase The nuclear membrane begins to reform DNA begins to decondense

22 Cytokinesis The two cells divide One parent cell becomes two daughter cells

23 Mitosis

24 Diploid vs. Haploid Haploid = n = half of the necessary genetic info needed to make an organism 2(n) = diploid, complete set of genetic material –Homologous chromosomes are 2(n) –Humans have a diploid number of 46!

25 Diploid vs. Haploid Cells that are haploid are: –Specialized sex cells such as sperm and egg cells in animals, and pollen and egg cells in plants Cells that are diploid include: EVERYTHING ELSE!! -such as zygote, muscle, blood, skin, many plant cells

26 Meiosis A process similar to mitosis except that the end product is a haploid (n) gamete Generation of a haploid gamete ensures that there will not be too many chromosome copies in offspring There are two stages of meiosis (I and II)

27 Meiosis Diploid (2n)  haploid (n)Diploid (2n)  haploid (n) Meiosissexual reproduction.Meiosis and FERTILIZATION = sexual reproduction.

28 Biological Relationship of Mitosis and Meiosis Mitosis Growth Meiosis Gametes n ♀ Egg ♂ Sperm Zygote 2n Cell Cycle

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30 Meiosis I Differences from mitosis: -centromeres remain intact and pairs separate, not sister chromatids -The chromosome remains in the sister chromatid form

31 Meiosis II -Similar to mitosis except chromosomes start with sister chromatids from meiosis I. The sister chromatids are not made in interphase like in mitosis.

32 Meiosis II continued

33 Ploidy of gametes during meiosis Female Male

34 Meiosis

35 Comparison of meiosis and mitosis

36 Late Prophase I Metaphase I Anaphase I Interphase II Telophase I Prophase IIMetaphase II Anaphase II Telophase II Cytokinesis

37 Syngamy – the union of two gametes

38 Chromosomes seemed to be the genetic material that carries the factors predicted by Mendel because: 1.They exist in pairs 2.They segregate 3.One of each pair of homologues is inherited 4.One of each pair is inherited from each parent 5.They assort randomly in meiosis

39 Additional diagrams of Meiosis

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41 Variation Meiosis results in variation amongst organisms –Crossing over of the chromosomes during Prophase I –Random rearrangement of chromosomes during Metaphase I and Anaphase I -Random fertilization of gametes (sperm & egg)

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