these slides contains different stages of mitosis and meiosis,what is Mitosis meiosis,i tried our level best to make it. hope you will learn it

1. Mitosis and Meiosis
Cell Division

2. Why Do Cells Divide?
For growth, repair, and
reproduction

3. Mitosis
•Organisms grow by the
addition of cells
•In multicellular organism some
of these cells perform
functions different from other
cells.
03_MAR_18 3ch dinesh

4. •The process of a cell becoming
different is differentiation.
•Under normal conditions once an
animal cell becomes specialized it
can no longer form an entire
organism, however plant cells are
totipotent and any cell can form an
entire plant. 03_MAR_18 4ch dinesh

5. When do cells divide?
•Most limiting factor in size is the
size of the cell membrane.
•Cells must obtain nutrients
•as volume increases, cell surface
area does not increase as greatly
•larger cells require a larger surface
area for survival
03_MAR_18 5ch dinesh

6. Cell Division vs. Nuclear Division
• Cytokinesis: The actual division of the cell into two new cells.
• Mitosis: The division of the nucleus of the cell into two new nuclei.
• Note: Sometimes cells go through mitosis without going through
cytokinesis. Describe a cell that did this.
03_MAR_18 6ch dinesh

7. Terminology
•Chromatin - thin fibrous form
of DNA and proteins
•Sister chromatids- identical
structures that result from
chromosome replication,
formed during S phase
03_MAR_18 7ch dinesh

8. Anatomy of a Chromosome
• Centromere - point
where sister chromatids
are joined together
• P=short arm; upward
• Q=long arm;
downward
• Telomere-tips of
chromosome
p -arm
centromere
q-arm
telomerechromatids 03_MAR_18 8ch dinesh

9. 03_MAR_18 9ch dinesh

10. How Do Cells Divide?
•Cell cycle - sequence of phases
in the life cycle of the cell
03_MAR_18 10ch dinesh

11. Getting ready to split
• Cell cycle has two parts:
• growth and preparation
(interphase)
• cell division
• mitosis (nuclear division)
• cytokinesis (cytoplasm division)
03_MAR_18 11ch dinesh

12. Interphase
•Occurs between divisions
•Longest part of cycle
•3 stages
03_MAR_18 12ch dinesh

13. 03_MAR_18 13ch dinesh

14. Interphase
•G1 or Gap 1
•The cell just finished
dividing so in Gap 1 the
cell is recovering from
mitosis
03_MAR_18 14ch dinesh

15. Interphase
•S or Synthesis stage
•DNA replicates
03_MAR_18 15ch dinesh

16. Interphase
•G 2 or Gap 2
•This is preparation
for mitosis
•Organelles are
replicated.
•More growth occurs.
03_MAR_18 16ch dinesh

17. 03_MAR_18 17ch dinesh

18. MITOSIS
Mitosis begins after G 2 and ends
before G 1
03_MAR_18 18ch dinesh

19. Prophase
•Chromosome
condense
•Microtubles form
•The nuclear envelope
breaks down
03_MAR_18 19ch dinesh

20. Metaphase
•Chromosomes are
pulled to center of
cell
•Line up along
“metaphase plate”
03_MAR_18 20ch dinesh

21. 03_MAR_18 21ch dinesh

22. Anaphase
•Centromeres divide
•Spindle fibers pull one
set of chromosomes to
each pole
•Precise alignment is
critical to division
03_MAR_18 22ch dinesh

23. 03_MAR_18 23ch dinesh

24. Telophase
•Nuclear envelope form around
chromosomes
•Chromosomes uncoil
•Cytokinesis
• animals - pinching of plasma membrane
• plants- elongates and the cell plate
forms( future cellwall and cell
membrane)
03_MAR_18 24ch dinesh

25. Meiosis
03_MAR_18 25ch dinesh

26. What is Meiosis?
A division of the nucleus that reduces
chromosome number by half.
•Important in sexual reproduction
•Involves combining the genetic
information of one parent with that of
the the other parent to produce a
genetically distinct individual
03_MAR_18 26ch dinesh

27. Terminology
•Diploid - two sets of
chromosomes (2n), in humans 23
pairs or 46 total
•Haploid - one set of
chromosomes (n) - gametes or sex
cells, in humans 23 chromosomes
03_MAR_18 27ch dinesh

28. Chromosome Pairing
•Homologous pair
• each chromosome in pair are
identical to the other ( carry
genes for same trait)
• only one pair differs - sex
chromosomes X or Y
03_MAR_18 28ch dinesh

29. Phases of Meiosis
•A diploid cell replicates its
chromosomes
•Two stages of meiosis
• Meiosis I and Meiosis II
• Only 1 replication
03_MAR_18 29ch dinesh

30. 03_MAR_18 30ch dinesh

31. •Synapsis - pairing of
homologous chromosomes
forming a tetrad.
•Crossing over - chromatids
of tetrad exchange parts.
03_MAR_18 31ch dinesh

32. Meiosis I

33. Prophase I
• Chromosomes condense
• Homologous chromosomes pair w/ each
other
• Each pair contains four sister chromatids
- tetrad
03_MAR_18 33ch dinesh

34. Metaphase I
•Tetrads or
homologous
chromosomes
move to center
of cell
03_MAR_18 34ch dinesh

35. Anaphase I
•Homologous
chromosomes
pulled to
opposite poles
03_MAR_18 35ch dinesh

36. Telophase I
•Daughter
nuclei formed
•These are
haploid (1n)
03_MAR_18 36ch dinesh

37. Meiosis II
•Daughter cells undergo a second
division; much like mitosis
•NO ADDITIONAL
REPLICATION OCCURS
03_MAR_18 37ch dinesh

38. Prophase II
•Spindle fibers
form again
03_MAR_18 38ch dinesh

39. Metaphase II
•Sister
chromatids
move to the
center
03_MAR_18 39ch dinesh

40. Anaphase II
•Centromeres
split
•Individual
chromosomes
are pulled to
poles
03_MAR_18 40ch dinesh

41. Telophase II & Cytokinesis
•Four haploid
daughter cells
results from
one original
diploid cell
03_MAR_18 41ch dinesh

42. Review Mitosis & Meiosis
•Both are forms of nuclear division
•Both involve replication
•Both involve disappearance of the
nucleus, and nucleolus, nuclear
membrane
•Both involve formation of spindle
fibers
03_MAR_18 42ch dinesh

43. DIFFERENCES
•Meiosis produces daughter cells that
have 1/2 the number of chromosomes
as the parent. Go from 2n to 1n.
•Daughter cells produced by meiosis are
not genetically identical to one another.
•In meiosis cell division takes place
twice but replication occurs only once.
03_MAR_18 43ch dinesh

44. Value of Variation
•Variation - differences between
members of a population.
•Meiosis results in random
separation of chromosomes in
gametes.
•Causes diverse populations that over
time can be stronger for survival.
03_MAR_18 44ch dinesh