2. MEIOSIS 3. MEIOSIS Meiosis is a special type of cell
divisionnecessary for sexual reproduction ineukaryotes. Meiosis
reduces the chromosome numberby half results in the production of
haploiddaughter cells. It involves two sequential cycles of
nuclearand cell division called meiosis I andmeiosis II 4. MEIOSIS
I It is also called the reductiondivision, here reduction
ofchromosome number takes place.Meiosis I contained 4 stages,1.
prophase2. metaphase3. anaphase4. telophase 5. Prophase I Longest
phase in meiosis. Sub divided into 5 phases based onchromosomal
behaviour,1.Leptotene2.Zygotene3.Pachytene4.Diplotene5.Diakinesis
6. prophase 7. Metaphase I Spindle formatuon is completede.
Chromosomes are arranged at theequater of spindle. 8. Anaphase I
Chromosomes are move alone withspindle towards the poles. At the
end of anaphase the diploidnumber of chromosomes is redused
intohaploid condition. 9. Telophase I The nuclear membrane and
nucleolusreappear. Cytokinesis follows and this is called asdiade
of cell. 10. Meiosis II Also called equational division. Meiosis II
contains 4 phases they are,1. Prophase II2. Metaphase II3. Anaphase
II4. Telophase II 11. Prophase II Sister chromatids of each
chromosomebeing to condence. The nucleolus and nuclear
envelopedisappear in both nuclei. Spindle fibres are formed. 12.
Metaphase II The spindle formation is completed. Chromosomes align
at the equator. 13. ANAPHASE II The division of centromere takes
placelongitudinally. The chromatides separate and go to theopposite
pole. 14. Telophase II The four group of chromosomes on reaching
thepoles organise into four daughter nuclei. Nuclei and nuclear
envelop are appear. Each nucleus has haploid number ofchromosomes.
Chromosomes recognize into chromatin fibres. 15. Cytokinesis The
cell itself is divided into two daughtercells by a separate process
calledcytokinesis. In animal cell cytokinesis is done theappearance
of a furrow in he plasmamembrane. The furrow graduallydisappear and
ultimately joins in thecenter dividing the cell cytoplasm
intotwo.
