3. MEIOSIS
• Meiosis is a special type of cell division
necessary for sexual reproduction in
eukaryotes.
• Meiosis reduces the chromosome number
by half results in the production of haploid
daughter cells.
• It involves two sequential cycles of nuclear
and cell division called meiosis I and
meiosis II
4.
5. MEIOSIS I
It is also called the reduction
division, here reduction of
chromosome number takes place.
Meiosis I contained 4 stages,
1. prophase
2. metaphase
3. anaphase
4. telophase
6.
7. Prophase I
• Longest phase in meiosis.
• Sub divided into 5 phases based on
chromosomal behaviour,
1.Leptotene
2.Zygotene
3.Pachytene
4.Diplotene
5.Diakinesis
9. Metaphase I
Spindle formatuon is completede.
Chromosomes are arranged at the
equater of spindle.
10. Anaphase I
Chromosomes are move alone with
spindle towards the poles.
At the end of anaphase the diploid
number of chromosomes is redused into
haploid condition.
11. Telophase I
The nuclear membrane and nucleolus
reappear.
Cytokinesis follows and this is called as
diade of cell.
12. Meiosis II
• Also called equational division.
• Meiosis II contains 4 phases they are,
1. Prophase II
2. Metaphase II
3. Anaphase II
4. Telophase II
13.
14. Prophase II
• Sister chromatids of each chromosome
being to condence.
• The nucleolus and nuclear envelope
disappear in both nuclei.
• Spindle fibres are formed.
15. Metaphase II
• The spindle formation is completed.
• Chromosomes align at the equator.
16. ANAPHASE II
• The division of centromere takes place
longitudinally.
• The chromatides separate and go to the
opposite pole.
17. Telophase II
• The four group of chromosomes on reaching the
poles organise into four daughter nuclei.
• Nuclei and nuclear envelop are appear.
• Each nucleus has haploid number of
chromosomes.
• Chromosomes recognize into chromatin fibres.
18. Cytokinesis
• The cell itself is divided into two daughter
cells by a separate process called
cytokinesis.
• In animal cell cytokinesis is done the
appearance of a furrow in he plasma
membrane. The furrow gradually
disappear and ultimately joins in the
center dividing the cell cytoplasm into
two.
