Mitosis produces two daughter cells through one cell division in somatic cells and maintains the same ploidy level (before and after are both diploid). Meiosis produces four daughter cells through two cell divisions in sex cells and reduces the ploidy level by half (before is diploid, after are haploid). Crossing over and independent assortment in meiosis I contributes to genetic variation in the gametes.

1. Prepared by:
Ms. Jasmine Nikki M. Versoza

2. 1. What are the phases of meiosis?
2. What type of cells are made during meiosis?
3. How many chromosomes do sperm cells
have? How about egg cells?
4. In what phase does crossing over happens?
5. What happens during the crossing over of
chromosomes?
6. What causes the variety in genes?

3. The union of two sex cells that
contain one set of chromosome
each and comes from two
individual organisms

4. If the reproductive cycle is to continue, then
the diploid cell must reduce its number of
chromosome sets before fertilization, or
there will be a continual doubling to
fertilization in the number of chromosome
sets in every generation.

5.  The number of sets of
chromosomes in a cell
 Haploid and Diploid

6. The type of cell division
taking place in sex cells. It
results in haploid
chromosome number.

7.  Reduction stage
 Synapsis, Crossing over,
and Independent
Assortment happens during
this stage

8. Prophase I
Metaphase I
Anaphase I
Telophase I

9.  First mechanism that
introduces variation into the
gametes happens here
 Synapsis and Crossing Over

10.  Pairing of the homologous chromosomes
 Homologous chromosomes have the same
length, staining pattern, and centromere
position
 A paired homologous chromosome is
composed of four sister chromatids known
as tetrad.

11. Process wherein homologous
chromatids exchange genetic
material to ensure variety in
gamete formation

13.  The tetrads line up along the
metaphase plate or equatorial
plate of the cell
 Spindle fiber increase in
number

14.  The second mechanism that
introduces gamete variation happens
here
 Independent or Random Assortment
– the arrangement of the tetrads at the
metaphase plate is at random

15.  Homologous chromosomes separate and
migrate toward their respective poles
 In humans, since there are 46
chromosomes, 23 will move to the poles,
which means that only half of the number
of chromosomes will remain in each cell

16.  The two daughter cells are completely
divided
 An equal amount of chromosomes are
found in both cells
 A nuclear envelope and nuclei reappear
and the chromosomes become less visible

17. Why is meiosis I called the
reduction stage?
The ploidy level has been
reduced from two to one

18.  A short pause between meiosis
I and meiosis II
 No replication of the
chromosomes happen here

19.  Division stage.
 Produces four genetically
unique cells
 More analogous to mitosis

20. The division of the two
daughter cells with haploid
chromosome numbers
produced in meiosis I

21. Prophase II
Metaphase II
Anaphase II
Telophase II

23. 1. What are the phases of meiosis?
2. What type of cells are made during meiosis?
3. How many chromosomes do sperm cells
have? How about egg cells?
4. In what phase does crossing over happens?
5. What happens during the crossing over of
chromosomes?
6. What causes the variety in genes?

24. COMPARING MITOSIS
AND MEIOSIS
LET’S DO THIS!

26. Meiosis
Prophase I (2N)
Mitosis
Prophase (2N)
XX
XX
XX
X
X
X
X
X
X
X - chromosome

27. Meiosis
Metaphase I (2N)
Mitosis
Metaphase (2N)
X - chromosome
XX
XX
XX
X
X
X
X
X
X

28. X
X
X
Meiosis
Anaphase I (2N)
Mitosis
Anaphase (2N)
X - chromosome
X
X
X
>
<
<
<
<
<
>
>
>
>
>
<

29. X
X
X
Meiosis
Telophase I (2N)
Mitosis
Telophase (2N)
>
<
<
<
<
<
X - chromosome
X X
X
>
>
>
>
>

30. Meiosis
Cytokinesis I (N)
Mitosis
Cytokinesis (2N)
X - chromosome
X
X
X
X
X
X
<
< <
<
<
<
< <
<
<

31. MITOSIS:
PARENT CELL VS. DAUGHTER CELLS
CHECK THIS OUT:

32. Mitosis
Prophase (2N)
Mitosis
Cytokinesis (2N)
X
X
X
X
X
X
X - chromosome
<
< <
<
<
<
< <
<
<

33. MEIOSIS II
GOING BACK…

34. X
X
X
X
X
X
Meiosis
Prophase II (N)
X - chromosome

35. Meiosis
Metaphase II (N)
X - chromosome
X
X
X
X
X
X

36. Meiosis
Anaphase II (N)
X - chromosome
>
<
<
<
>
>
>
<
<
<
>
>

37. X - chromosome
>
<
<
<
>
>
Meiosis
Telophase II (N)
>
<
<
<
>
>

38. X - chromosome
< <
<
<
<
Meiosis
Cytokinesis II (N)
< <
<
<
<

39. MEIOSIS:
PARENT CELL VS. DAUGHTER CELLS
CHECK THIS OUT:

40. Meiosis
Prophase I (2N)
Meiosis
Cytokinesis II (N)
X - chromosome
< <
<
< <
< <
< < <
XX
XX
XX

41. WHY DOES MEIOSIS
RESULT IN HAPLOID
CHROMOSOME NUMBERS
FOR EACH DAUGHTER
CELL?
HMMM….

42. Meiosis
Prophase I (2N)
Meiosis
Cytokinesis II (N)
X - chromosome
< <
<
< <
< <
< < <
XX
XX
XX

43. EVEN IF THE CHROMOSOMES OF THE
FOUR DAUGHTER CELLS IN MEIOSIS
DUPLICATE DURING S PHASE, IT WILL
STILL RESULT IN HAPLOID
CHROMOSOME NUMBER. HOW COME
THE PARENT CELL HAS A DIPLOID
CHROMOSOME NUMBER?
HMMM….

45. 1. If n=4 for fruit flies, how many
chromosome does a wing cell have?
2. If the 2n= 86 for a pine tree, how
many chromosomes does it have in
its ovum?

46. Complete the table below.
Mitosis Meiosis
Number of Daughter Cells
Number of Cell Division Happening
Type of cell where it is taking place
Ploidy Level (Before)
Ploidy Level (After)