Mais conteúdo relacionado Semelhante a Chapter 5 with ans (20) Mais de Gabriel Chua (20) Chapter 5 with ans1. 1 © Gabriel Chua, 2013
Chapter 5: Cell Division
Important terms and concept
1. Haploid – Cell with single set of chromosome (n)
2. Diploid – Cell with complete sets of chromosomes (2n)
3. Cell division:
a) Mitosis – 1 parent cell (2n) 2 identical daughter cells ( 2n )
b) Meiosis – 1 parent cell (2n) 4 different daughter cells ( n )
4.
5.1) Mitosis
1. 1 parent cell (2n) 2 identical daughter cells ( 2n )
2. It is part of the cell cycle (Interphase Mitosis Cytokinesis)
3. Interphase is divided into:
a) G1 phase Growth of cell by producing proteins and organelles
b) S phase Synthesis / duplication of DNA (thread-like chromatin)
c) G2 phase Growth of cell by producing proteins and organelles
4. Mitosis is divided into prophase, metaphase, anaphase and telophase
chromatid sister chromatid
chromosome chromosome
homologous chromosome
2. 2 © Gabriel Chua, 2013
Prophase Chromosomes start to appear and condense as 2
identical chromatids
Nuclear membrane disintegrate and nucleolus
disappear
Centrioles move apart to opposite sides
Spindle fibre begins to form
Metaphase Chromosomes move to cell’s equator
Chromosomes line up at cell’s equator with centromeres
attached to spindle fibre
Each chromatid faces its own pole
Anaphase Chromosomes divide into two
Each sister chromatid 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
5. Cytokinesis in animal cells is by forming cleavage while that of plant cells is by forming
cell plate.
6. Importance of mitosis
a) Repair damaged cells and replace dead cells
b) Asexual reproduction in unicellular organisms
c) Preserve diploid number of chromosome
d) Ensure new cells are identical to parent cells
3. 3 © Gabriel Chua, 2013
7. Application of mitosis
a) Repair damaged cells and replace dead cells
b) Tissue culture
c) Clonnnig
d) Uncontrolled mitosis causes cancer
5.2) Meiosis
1. 1 parent cell (2n) 4 different daughter cells ( n )
2. Meiosis is divided into:
a) Meiosis I b) Meiosis II
Prophase I Prophase II
Metaphase I Metaphase II
Anaphase I Anaphase II
Telophase I Telophase II
Prophase I Chromosomes thickens and condense
Each chromosome consists of 2 sister chromatids
Homologous chromosomes pair together (bivalent) via
synapsis
The criss-cross between homologous chromosomes is
known as chiasmata
This results in genetic variation
Centrioles move to opposite poles
Spindle fibre forms
Nuclear membrane and nucleolus disintegrate
Metaphase I Paired homologous chromosomes line up at cell’s
equator
Each chromosome are attached to spindle fibre at
centromeres
Each chromosome faces its own pole
Anaphase I Paired homologous chromosomes separate from each
other and move to opposite pole
4. 4 © Gabriel Chua, 2013
Telophase I Chromosomes reached its own pole
Each pole has haploid chromosome set
Spindle fibre disappear
Nuclear membrane and nucleolus reform
Cytokinesis begins
3. Meiosis II is the same as mitosis
4. Importance of meiosis
a) Allow trait inheritance in offspring
b) Maintain same number of chromosomes in each generation
c) Ensure production of haploid gametes in sexual reproduction
d) Produce genetic variation
Comparison between Meiosis I and Meiosis II
Meiosis I Meiosis II
Similarities
1. Consists of 4 stages, ie. prophase, metaphase, anaphase & telophase
2. Involves division of nucleus and cytoplasm
Differences
Yes, at Prophase I Synapsis No
Yes, at Prophase I Crossing over No
In metaphase I, paired
homologous chromosomes /
bivalent / tetrad line up at
equator
Metaphase
In metaphase II, sister
chromatids line up at equator
In anaphase I, homologous
chromosomes separate and
move to opposite side
Anaphase I
In anaphase II, sister
chromatids separate and
move to opposite side
2 different daughter cells ( n )
Number of daughter cells
4 different daughter cells ( n )
5. 5 © Gabriel Chua, 2013
Comparison between Meiosis and Mitosis
Meiosis Mitosis
Similarities
1. Both process are cell division process
2. Chromosomes only replicate once
Differences
Reproductive cells Place occur Somatic cells
Parent cells divide twice Number of division Parent cells divide once
4 different daughter cells (n) Number of daughter cells 2 identical daughter cells
(2n)
Yes, at Prophase I Synapsis No
2 Number of cytokinesis 1
Yes, at Prophase I Crossing over No
Each daughter cell has half
the number of chromosome
of parent cell
Number of chromosomes in
daughter cells
Each daughter cell has the
complete number of
chromosome as parent cell
Genetic composition are
different to parent cell or to
each other
Genetic composition of
daughter cells
Genetic composition are
identical to parent cell and
each other
Occurs during interphase
before Meiosis I begins DNA replication
Occurs during interphase
before mitosis begins
Produce gametes
Cause genetic variation
Reduce number of
chromosomes to half
Role in animal body
Produce cells for
growth
Asexual reproduction