Cellular Division

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 http://www.yorku.ca/kdenning/images/bioanthropology/chromosome.jpg

4. Mitosis – Somatic Line • Mitosis http://staff.kings.edu/kdils/StudentWork/Kalinay%20Lessons/lesson_plan_3_files/image007.jpg

5. Mitosis 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) http://kvhs.nbed.nb.ca/gallant/biology/mitosis_phases.jpg

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 http://kvhs.nbed.nb.ca/gallant/biology/mitosis_phases.jpg

7. Mitosis Stages - Metaphase • DNA lines up along equator of cell http://kvhs.nbed.nb.ca/gallant/biology/mitosis_phases.jpg

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 http://kvhs.nbed.nb.ca/gallant/biology/mitosis_phases.jpg

9. Mitosis Stages - Telophase • Cell begins to pinch in along the equator of the cell • Nucleus begins to form • Mitosis http://kvhs.nbed.nb.ca/gallant/biology/mitosis_phases.jpg

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) http://kvhs.nbed.nb.ca/gallant/biology/mitosis_phases.jpg

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 • Meiosis http://www.accessexcellence.org/RC/VL/GG/meiosis.php

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) http://www.dnaletters.com/img/3.gif http://www.realscienceprograms.com/files/IMAGES/egg_cell.jpg

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 http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpg http://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg

14. Meiosis Stages - Metaphase I • Replicated chromosomes of DNA lines up along equator of cell http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpg http://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg

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 http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpg http://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg

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 http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpg http://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg

17. Meiosis Stages - Prophase II • Spindle fibers form and attach to DNA http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpg http://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg

18. Meiosis Stages - Metaphase II • DNA lines up along equator of cell http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpg http://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg

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 http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpg http://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg

20. Meiosis Stages - Telophase II • Cells begins to pinch in along the equator of the cell • Nucleus begins to form http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpg http://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg

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) http://scienceprofonline.googlepages.com/meiosis.jpg/meiosis-full.jpg http://www.ri.net/schools/Narragansett/NHS/mywebpage/meiosis.jpg

22. Fertilization (Humans) • Egg with 23 chromosomes • Sperm with 23 chromosomes • Fertilization – zygote with 23 PAIR of chromosomes! • TA DA! (Sea Urchins) http://www.brown.edu/Courses/BI0032/gentherp/pronucl.jpg

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