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Cellular Division Mitosis Meiosis. Chromosomes Humans have 23 pairs of chromosomes 1 set inherited from mother 1 set inherited from father https://bioinformatics.cs.vt.edu/~heath/IMAGES/human_chromosomes.gif.

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Presentation on theme: "Cellular Division Mitosis Meiosis. Chromosomes Humans have 23 pairs of chromosomes 1 set inherited from mother 1 set inherited from father https://bioinformatics.cs.vt.edu/~heath/IMAGES/human_chromosomes.gif."— Presentation transcript:

1 Cellular Division Mitosis Meiosis

2 Chromosomes Humans have 23 pairs of chromosomes 1 set inherited from mother 1 set inherited from father https://bioinformatics.cs.vt.edu/~heath/IMAGES/human_chromosomes.gif

3 Chromosome DNA is called chromatin when in cell during normal functioning of cell – cannot discern anything except nucleolus DNA replicates When cell divides, DNA condenses into tight “X” shape, one side the original and the other side copied DNA

4 Mitosis – Somatic Line Mitosis

5 Mitosis Stages - Interphase Cell spends most of its life in interphase (G1) Signaled to replicate DNA (S phase)replicate Cell resumes normal functions with replicated DNA (G2)

6 Mitosis Stages - Prophase DNA condenses Spindles form (they organize and guide DNA as it separates to each side of the cell Nucleus begins to dissolve Spindle fibers attach DNA

7 Mitosis Stages - Metaphase DNA lines up along equator of cell

8 Mitosis Stages - Anaphase Spindle fibers attached to DNA shorten and DNA moves to one side of the cell Notice that arms of the chromosome separate

9 Mitosis Stages - Telophase Cell begins to pinch in along the equator of the cell Nucleus begins to form Mitosis

10 Mitosis Stages – Interphase – 2 cells Cell spends most of its life in interphase (G1) Signaled to replicate DNA (S phase) Cell resumes normal functions with replicated DNA (G2)

11 Meiosis – Germ Line Sexual Reproduction In humans – 23 pairs of chromosomes, or a total of 46 chromosomes  1 chromosome from mother  1 chromosome from father Meiosis

12 Meiosis Stages - Interphase Cell spends most of its life in interphase (G1) Signaled to replicate DNA (S phase) Cell resumes normal functions with replicated DNA (G2)

13 Meiosis Stages – Prophase I DNA condenses Replicated DNA from adjoining chromosomes crossover Spindles form (they organize and guide DNA as it separates to each side of the cell Nucleus begins to dissolve Spindle fibers attach DNA

14 Meiosis Stages - Metaphase I Replicated chromosomes of DNA lines up along equator of cell

15 Meiosis Stages - Anaphase I Spindle fibers attached to chromosome DNA shorten and one of the pairs of chromosome of DNA moves to one side of the cell – or the other Chromosome number in humans – 23 – no longer in pairs

16 Meiosis Stages – Telophase I Cell begins to pinch in along the equator of the cell Division not yet complete NOTE – cells now only have half the chromosome number

17 Meiosis Stages - Prophase II Spindle fibers form and attach to DNA

18 Meiosis Stages - Metaphase II DNA lines up along equator of cell

19 Meiosis Stages - Anaphase II Spindle fibers attached to DNA shorten and DNA moves to one side of the cell Notice that arms of the chromosome separate

20 Meiosis Stages - Telophase II Cells begins to pinch in along the equator of the cell Nucleus begins to form

21 Meiosis Stages – Interphase – 4 cells Cell spends most of its life in interphase (G1) Signaled to replicate DNA (S phase) Cell resumes normal functions with replicated DNA (G2)

22 Fertilization (Humans) Egg with 23 chromosomes Sperm with 23 chromosomes Fertilization – zygote with 23 PAIR of chromosomes! TA DA! (Sea Urchins) TA DA!

23 Questions? BJ Shaw Panochthus frenzelianus American Museum of Natural History 2004


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