LEADING TO MITOSIS AND MEIOSIS

1. Leading to
Mitosis & Meiosis
by
Muhammad Iqbal Khan
SS Biology
Email ID:mikhan1313@yahoo.com

2. http://biotech-adventure.okstate.edu/low/basics/mitosis/mitosis-diagram/diagram.gif

3. Cell Cycle
http://www.bmb.psu.edu/courses/biotc489/notes/cycle.jpg

4. Mitosis
• One type of cell division
Cell process in which the nucleus
divides to form two nuclei identical to
each other, and identical to the
original nucleus, in a series of steps
(prophase, metaphase, anaphase, and
telophase)

5. Mitosis allows for growth
and replaces worn out or
damaged cells.

6. Interphase
• Period of growth & development
• Hereditary information (DNA)
copied (replicated / duplicated)
• Cells that do not divide (nerves)
are always in interphase

7. http://biotech-adventure.okstate.edu/low/basics/mitosis/phases/interphase/interphase.gif

8. Prophase
•DNA begins to shorten & thicken
–Now called chromatids /
chromosomes
•Centromeres form
•Nuclear membrane breaks apart
•Spindle fibers form

9. http://biotech-adventure.okstate.edu/low/basics/mitosis/phases/prophase/prophase.gif

10. Metaphase
•Chromatids / chromosomes
line up
•Centromere attaches to
spindle fibers

11. http://biotech-adventure.okstate.edu/low/basics/mitosis/phases/metaphase/metaphase.gif

12. Anaphase
•Centromeres divide
•Spindle fibers shorten
•Chromatid pairs separate – move
to ends of cell
•Chromatids are now called
–Each ½ of the pair is now called a
chromosome

13. http://biotech-adventure.okstate.edu/low/basics/mitosis/phases/anaphase/anaphase.gif

14. Telophase
•Spindle fibers disappear
•Chromosomes uncoil
•Nuclear membrane forms
•Cell divides (cytokinesis)

15. http://biotech-adventure.okstate.edu/low/basics/mitosis/phases/telophase/telophase.gif

16. Interphase Prophase
Metaphase Anaphase
Telophase Interphase
http://biology.nebrwesleyan.edu/benham/mitosis/

17. Mitosis Animation
http://www.johnkyrk.com/mitosis.html

18. Results of Mitosis
• Division of nucleus
–Nuclei are identical to each other
•Same number & type of chromosomes

19. Asexual Reproduction
A type of reproduction - fission,
budding, and regeneration - in
which a new organism is produced
from one parent and has DNA
identical to the parent organism.

20. Asexual Reproduction
•Offspring produced from one
organism
•Hereditary information is
identical
•Mitosis is one form of asexual
reproduction

21. Sexual Reproduction
Meiosis

22. Sexual Reproduction
A type of reproduction in which
two sex cells, usually an egg and
a sperm, join to form a zygote,
which will develop into a new
organism with a unique identity.

23. Sexual reproduction
results in a great variety,
or diversity, of offspring.

24. Meiosis
• The nucleus divides twice
– Meiosis I
– Meiosis II

25. http://biotech-adventure.okstate.edu/low/basics/meiosis/diagram/

26. Interphase
• DNA is duplicated

27. Prophase I
• DNA shorten & thicken
– Forms chromatids / chromosomes

28. http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/prophase/leptotene/leptotene.gif

29. Metaphase I
•Copied chromatids /
chromosomes line up in
middle of cell
•Centromeres attach to
spindle fibers

30. http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/metaphase-I/metaphase-I.gif

31. Anaphase I
•Chromatid pairs are pulled
apart
–They DO NOT separate
•Move to ends of cell

32. http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/anaphase-I/anaphase-i.gif

33. Telophase I
•Cell divides
•No further replication of
hereditary material

34. http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/telophase-I/telophase-I.gif

35. There are now two
cells. Both cells have
full sets of genetic
material
(chromosomes)

36. Prophase II
•Similar to mitosis
–Starts with TWO cells instead
of one
•Spindle fibers appear

37. http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/prophase-II/prophase-II.gif

38. Metaphase II
•Duplicated chromatid /
chromosomes line up in
middle of cell
•Spindle fibers attach to
centromeres

39. http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/metaphase-II/metaphase-II.gif

40. Anaphase II
•Centromere divides
–Chromatids separate & move
to ends of cell
•Chromatids are now individual
chromosomes

41. http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/anaphase-II/anaphase-II.gif

42. Telophase II
•Spindle fibers disappear
•Nuclear membranes form at
each end of cell
•Cells divide
–Results in 4 cells
•Each with ½ the original number
of chromosomes

43. http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/telophase-II/telophase-II.gif

44. Meiosis Animation
http://www.johnkyrk.com/meiosis.html

45. In summary:
Meiosis
• Two cells form during meiosis I
• In meiosis II, both of these cells
form two cells
• The two divisions of the nucleus
result in four sex cells (gametes)
• Each has one-half the number of
chromosomes in its nucleus that was
in the original nucleus