Meiosis occurs in 2 stages – Meiosis 1 and Meiosis 2. It requires 1 round of replication of DNA and two rounds of chromosomal
segregation. Meiosis 1 is division reduction and meiosis 2 is a division equation. DNA replication followed by cell division occurs in
meiosis 1 and cell division only occurs in meiosis 2.
This kind of cell division occurs to reduce the chromosome number by half. It is involved in the production of haploid daughter cells.
Meiosis is divided into two phases. Meiosis I and meiosis II.
Meiosis I
Prophase I: Prophase I is the first phase of meiosis I. Prophase I has five phases based on chromosomal behavior. They are
Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis.
Leptotene: The chromosome undergoes compaction.
Zygotene: The chromosome starts to pair with each other and this is called synapsis. The complex formed by the pair of the synapsed
chromosome is known as a bivalent or tetrad.
Pachytene: The bivalent chromosomes appear to be more prominent and are called tetrads. Diplotene: The chromosome appears to be
X in shape and is called chiasmata.
Diakinesis: The chiasmata termination occurs. The fully condensed chromosomes are formed and the meiotic spindle will get prepared
and assembled for the separation of Homologous chromosomes. The nucleolus will disappear and the nuclear envelope forms.
Metaphase I: The alignment of the bivalent chromosomes occurs on the equatorial plane.
Anaphase I: During this phase, the homologous chromosome gets separated but the sister chromatids will be attached to the
centromere.
Telophase l: The nuclear membrane as well as the nucleolus will reappear. Cytokinesis occurs and thus two daughter cells are formed.
Meiosis II
Prophase II, metaphase II, anaphase II, and telophase II will take place. At the end of the meiosis II, 4 haploid daughter cells will be
formed.
Prophase II: The chromosomes begin to condense followed by a nuclear membrane dissolution and the disappearance of the Golgi
apparatus and ER complex.
Metaphase II: The chromosomes also get aligned to shape the metaphase plate at the equator.
Anaphase II: The sister chromatids are pushed off to the opposite poles. As the chromatids move towards the poles the kinetochore is
at the leading edge with the dragging of the chromosomal arms.
Telophase II: The chromosomes dissolve again into an undifferentiated mass, and develop a nuclear envelope around it. Telophase II is
accompanied by cytokinesis and results in the creation of four haploid daughter cells.