Grade 8 Science ( BIOLOGY ) MITOSIS AND MEIOSIS

1. prayer

2. TERESITA M. PERUCHO
M
aster Teacher I- science
Mitosis &
Meiosis

3.  Compare mitosis and meiosis, and their
role in the cell-division cycle
S8LT-IV
d-16
 Explain the significance of meiosis in
maintaining the chromosome number
S8LT-IV
e-17
competency

4. OBJECTIVES
1. D
efine mitosis &meiosis
2. D
escribe the changes that occur
in each stage of mitosis &meiosis

6. CELL CYCLE
M
IT
O
SIS &
M
EIO
SIS

7. Guide
questions

8. Guide questions
What is
mitosis&
meiosis
Identify the stages of
mitosis ( in order ) ?
What are the four
important events that
happen during the cell
division?

9. What is mitosis& meiosis
M
itosis – cell division that happens in body
cells
M
eiosis – cell division that produces haploid sex
cells such as eggs and sperm cells

10. Interphase (g1 , s , g2 ) , prophase , metaphase
,anaphase , telophase and cytokinesis
Identify the stages of mitosis ( in order ) ?

11. 1. Cell growth
2. Chromosome replacement
3. Chromosome segregation
4. Cell division
W
hat are the four important events that
happen during the cell division?

12. cELL
- (from Latincella , meaning "small
room") is the basic structural, functional,
and biological unit of all known organisms.
Cells are the smallest units of life, and
hence are often referred to as the "building
blocks of life".
CYTOLOGY
– study of cell.

13. The cell cycle, or cell- division cycle, is the series of
events that take place in a cell that cause it to divide
into two daughter cells.
The cell cycle is a four- stage processin which the
cell increases in size (gap 1, or G1, stage), copies its
DNA (synthesis, or S, stage), prepares to divide (gap 2
or G2, stage), and divides (mitosis, or M, stage). The
stages G1, S, and G2 make up interphase, which
accounts for the span between cell divisions.

14. CELL CYCLE

15. INTERPHASE

16. INTERPHASE

17. INTERPHASE

19. MITOSIS
Mitosis – cell division that happens in
body cells

20. CHROMOSOMES

21.  Chromosomes now called
chromatids
because they doubled to form short thick
rods which pair up and line up in the
center of the nucleus.
 A centromere connects the two halves of
the doubled chromatids.
 Spindle fibers begin to form.
Spindle fiber
– a fibrous structure from the
cytoplasm which forms to the centriole.
 Centrioles move to opposite sides of the
cell.
 The nuclear membrane breaks down.
PROPHAS

22. METAPHASE
 Centromeres of the chromatid
pairs line up in the middle of
the cell.
 Metaphase plate
- location
where the centromeres line up
in the center of the cell.
 By the end of metaphase each
chromatid has attached to
spindle fibers.

23. ANAPHASE
 The spindle fibers pull the
chromatids apart.
 This separates each one
from its duplicate. These
move to opposite sides of
the cell.
 Now there are two
identical sets of
chromosomes.

24. TELOPHASE
 When the chromosomes
reach opposite sides of the
cell the spindle fibers break
up.
 The nuclear membrane begins
to reform.
 A furrow begins to develop
between the two sets of
chromosomes.

25. CYTOKINESIS
The two identical cells completely divide and the cell
membrane is completely formed.It is the division of the
cytoplasm

27. Meiosis– cell division that
produces haploid sex cells such
as eggs and sperm cells
 D
iploid (2n) - Acell with two of each
kind of chromosome.
 O
ne chromosome from each parent.
If two body cells were to combine
nuclei, the number of chromosomes
would double.
 In order for sexual reproduction to
occur, each cell involved must
reduce its chromosome number by
half.
 Haploid (n)- Acell with one of each
kind of chromosome.

28. HAPLOID CELLS

29. Homologous Chromosomes

30. MEIOSIS

31. STAGES OF MEIOSIS

32. PROPHASE 1
Tetrads are so tight that non
-
sister chromatids from the
homologous pair actually
exchange genetic material.
Crossing over
- The exchange
of genetic material by non
-
sister chromatids during late
prophase I of meiosis.
Results in a new combination
of alleles

33. METAPHASE 1
 Homologous chromosomes line
up together in pairs.
 * In mitosis homologous
chromosomes line up in the
middle independently of each
other.

34. ANAPHASE 1
 Spindle fibers attach to the
centromeres of each pair.
 Homologous chromosomes
separate and move to
opposite ends of the cell.
 Centromeres DO NOT split like
they do in mitosis
 Now each cell will get one
chromosome from each
homologous pair.

35. TELOPHASE 1
 Spindle fibers break down
 Chromosomes uncoil
 Cytoplasm divides
 Another cell division is needed
because the number of
chromosomes has not been
reduced
 After telophase I there maybe a
short interphase, but not always.
It is important to note that if a cell
does have a second interphase,
there is No replication of
chromosomes
.

36. MEIOSIS 1

37. MEIOSIS 2
 Is basically just like mitosis, but
remember the chromosomes did
not duplicate in interphase II.
 Prophase II
Chromosomes begin to line up in
the middle of the cell.
Spindle fibers begin to form
 M
etaphase II
Chromosomes line up on the
metaphase plate

38. MEIOSIS 1
 Anaphase II
Centromeres split
Sister chromatids separate and
move to opposite sides of the cell
 T
elophase II
Nuclei reform
Spindle fibers disappear
Cytoplasm divides into two.
T
he number of chromosomes in
each daughter cell has now been
reduced by half.

39. MEIOSIS 2

42. MITOSIS
(ASEXUAL )
MEIOSIS
(SEXUAL)
Number of daughter cells produced
Function
Chromosome number
Pairing of homologous chromosomes take
place. (Yes/No)
The daughter cells produced are always
identical in terms of genetic material.
(Yes/No)
creates
ASSIGNMENT
Complete the table.

43. MITOSIS
(ASEXUAL )
MEIOSIS
(SEXUAL)
Number of daughter cells produced 2 4
Function Cellular reproduction
( asexual) ; for growth &
repair of the body.
Sexual reproduction
Chromosome number diploid haploid
Pairing of homologous chromosomes take
place. (Yes/No)
NO YES
The daughter cells produced are always
identical in terms of genetic material.
(Yes/No)
YES NO
creates Somatic cells ( body cells) Sex cells ( gametes)
Complete the table.

44. Thank you