1. Interphase:

a) G1 Phase:

• period between the beginning of interphase and the beginning of the DNA synthesis.
• It is the longest phase and constitutes up to 50% of the total inter phase duration.
• Marked events includes Marked protein and RNA synthesis, Increase the cell volume by imbibing water and nutrients

b) S Phase:

• period between G1 and G2 phases
• DNA synthesis takes place (chromosomes replicate)
• RNA and protein synthesis are very low.

c) G2 Phase:

• period between S and M phases
• There is considerable amount of RNA and protein synthesis takes place in this phase.

2. M phase:

a) Interphase:

• Structural and functional protein is synthesized.
• RNA and ribosomes are synthesized.
• DNA of each chromosome replicates.
• Cell volume increases.
• Division of mitochondria and chloroplast.
• Doubling of centrioles
• High cell metabolic rate

b) Prophase:

• Uncoiling of chromatids
• Disintegration of nucleolus
• Disappearance of nuclear membrane
• Formation of spindle

c) Metaphase:

• Arrangement of chromosome on equilateral region.

d) Anaphase:

• Splitting of centromere or division of chromosome.
• Movement of chromosomes to opposite poles.

e) Telophase :

• Formation of daughter nuclei
• Reappearance of nuclear membrane and nucleolus.

3. Meiosis I:

A) Prophase I: Homologous chromosomes pairing (Synapsis) and crossing over (Recombination) occurs.

a) Leptotene: These cells and nuclei are usually bigger than the other cells, like a “bouquet”

b) Zygotene: Pairing of homologous chromosomes begins. It is also called synapsis and the resulting structure synaptic complex

c) Pachytene: The pairing stabilizes. The number of synaptic complexes corresponds to the number of chromosomes in a haploid set of the respective species. The pairs are also called bivalents.

d) Diplotene: The bivalents separate and formed cross-like structures, single or multiple loops: the chiasmata (sing. chiasma).

e) Diakinesis: The chromosomes condense and become more compact.

B) Metaphase I: Bivalents are randomly oriented along the metaphase plate.

C) Anaphase I:

• Kinetochore microtubules shorten and pull chromosome towards opposite poles forming two haploid chromosomal sets.
• Non-kinetochore microtubules lengthen pushing the centrioles apart and the cell elongates.

D) Telophase I:

• Microtubules disappears, new nuclear membrane surrounds each haploid set
• Chromosomes uncoil and cytokinesis occurs.

E) Interkinesis: Rest period of cell and hence no DNA replication occurs during this stage.

4. Meiosis II

• Results in formation of 4 haploid cells.

a) Prophase II:

• Disappearance of nucleoli and the nuclear envelope.
• Shortening and thickening of chromatids.
• Centrioles moves to the polar regions and arrange spindle fibers for the second meiotic division.

b) Metaphase II:

• Metaphase equatorial plate is rotated by 90 degrees when compared to meiosis I.

c) Anaphase II:

• Microtubules pull the sister chromatids towards opposite poles.

d) Telophase II:

• Uncoiling and lengthening of the chromosomes and the disappearance of spindle fiber.
• Nuclear envelops reform and cleavage and produces four daughter cells.