3.  Terms to take note and remember!!
 Haploid – Cells with single unpaired set of
chromosome (n)
 Diploid – Cells with two sets of chromosome (2n)
Sister
Chromatid chromatid
Chromosome Chromosome
Homologous
chromosome

4.  Cell division:
a) Mitosis (2n  2n) (1 parent cell  2 identical daughter
cells)
b) Meiosis (2n  n) (1 parent cell  4 different daughter
cells)
Mitosis Meiosis

5.  Mitosis (somatic cells)
 1 parent cell (2n)  2 identical daughter cells (2n)
1 parent cell (2n)
2 identical
daughter cells (2N)
 Interphase  Mitosis  Cytokinesis
Cell cycle

6. Cell cycle
G1 phase S phase
Growth of cell DNA
before DNA duplicates
duplicates
Cytokinesis G2 phase
Growth of cell
after DNA
duplicates
Mitosis

7. Prophase  Chromosomes start to appear and
condense as 2 identical chromatids
 Nuclear membrane breaks down and
nucleolus disappear.
 Centrioles move apart to opposite
poles
 Spindle fibre begins to form
Metaphase  Chromosomes move to cell’s equator
 Chromosomes line up along the
equator with centromeres attached to
spindle fibre
 Each chromatid faces it’s own pole

8. Anaphase  Chromosome divides into two
 Each sister chromatids separate and
move to opposite poles
 When the chromatids reached its own
pole, they become independent
chromosomes
Telophase  There are now 2 sets of
chromosomes, one at each pole
 Chromosomes become thread-like
structures
 Spindle fibre disappear
 Nuclear membrane begins to form
around both sets of chromosomes
 Nucleolus reappears
 Cytokinesis begins

9. Cytokinesis
cleavage
Animal cells
Cell plate
Plant cells

10. http://www.youtube.
com/watch?v=VGV3fv
-uZYI
Cell cycle

11.  Regulation and application of mitosis
a) Repair damaged cells and replace dead cells
b) Tissue culture
c) Clonning
d) Cancer (uncontrolled mitosis)
 Importance of mitosis
a) Repair damaged cells and replace dead cells
b) Asexual reproduction in unicellular organisms
c) Preserve diploid number of chromosomes
d) Ensure new cells are identical to parent cells

12.  Meiosis (reproductive cells)
 1 parent cell (2n)  4 daughter cells (n)
 Meiosis is divided into:
a) Meiosis I 1 parent
 Prophase I cell (2n)
 Metaphase I
 Anaphase I
 Telophase I
b) Meiosis II
 Prophase II
 Metaphase II Same as
 Anaphase II mitosis
 Telophase II
4 different daughter cells (n)

13. Prophase I  Chromosomes thicken and condense
 Each chromosome consists of 2 sister
chromatids
 Homologous chromosomes pair
together (bivalent) via synapsis.
 The criss-cross between homologous
chromosomes are known as chiasmata
 This results in genetic variation
 Centrioles move to opposite poles
 Spindle fibre forms
Chiasmata
 Nuclear membrane and nucleolus
disintegrate
Metaphase I  Paired homologous chromosomes line
up at equator of the cell
 Each chromosome are attached to
Homologous
spindle fibre at centromere
chromosome
 Each chromosome faces each own pole
undergoing
synapsis

14. Anaphase I  Paired homologous chromosomes
separate from one another and move
to opposite pole
Telophase I  Chromosomes reached their own pole
 Each pole has haploid chromosome set
 Spindle fibre disappear
 Nuclear membranes and nuclei reform
 Cytokinesis begins
Video of meiosis
http://www.youtube.com/wa
tch?v=kVMb4Js99tA

15.  Importance of meiosis
a) Allow trait inheritance in offspring
b) Maintain diploid number in each generation
c) Ensure production of haploid gametes in sexual
reproduction
d) Produce genetic variation

16.  Comparison between Meiosis I and II
Meiosis I Meiosis II
Similarities
1. Consists of 4 stages, ie. prophase, metaphase, anaphase and telophase
2. Involves division of nucleus and cytoplasm
Differences
Synapsis occur No synapsis
Crossing over occurs No crossing over
In metaphase I, paired homologous In metaphase II, sister chromatids line up at
chromosomes line up at equator equator
In anaphase I, paired homologous In anaphase II, sister chromatids separate
chromosomes separate and move to opposite and move to opposite poles
poles
At the end of meiosis I, 2 haploid cells are At the end of meiosis II, 4 haploid cells are
formed formed

17.  Comparison between Meiosis and Mitosis
Meiosis Mitosis
Similarities
1. Both process are cell division of cells
2. Chromosomes only replicate once
Differences
Aspects
Reproductive organs (testes Place occur In somatic cells
& ovary)
Parent cell divides twice No. of division Parent cells divides once
4 haploid (n) daughter cells No. of daughter cells 2 diploid (2n) daughter cells
Synapsis occur in prophase I Synapsis No synapsis
Twice No. of cytokinesis Once
Crossing over in prophase I Crossing over No crossing over
Each daughter cell has ½ the No. of chromosome in Each daughter cell has the
no. of chromosome of parent daughter cell same no. of chromosome as
cell parent cell

18. Differences
Aspects
Genetic composition are not Genetic composition of Daughter cells are genetically
identical to parent cell or to daughter cells identical to parent cell and
each other each other
Occurs during interphase DNA replication Occurs during interphase
before Meiosis I begins before mitosis begins
Produce gametes, causing Role in animal body Produce cells for growth,
genetic variation, reduce no. maintenance and repair
of chromosome into half body tissues