• Occurs in sex cells or gametes
• After undergoing meiosis, the chromosome
number of a cell is reduced by half
• Meiosis is necessary in the formation of male &
• Hence gametes have half the number of
chromosomes as compared to other normal cells
• Entire meiosis is composed of two parts: Meiosis I
& meiosis II
• In Meiosis I, a sex cell divides into two cells and
the chromosome number is halved
• It has 4 phases: Prophase I, Metaphase I,
Anaphase I & Telophase I
• Meiosis I is followed by meiosis II immediately
without the cell going into interphase
*Interphase is the duration between two successive mitotic/meiotic
phases consisting of 3 phases: G1, S & G2
• Longest and most complex phase (90%).
• Chromatin condenses to form chromosomes.
• Synapsis occurs: homologous chromosomes
come together to form a tetrad.
• Tetrad is two chromosomes or four chromatids
(sister and non-sister chromatids).
• Crossing over of genes occurs in the tetrad
*Homologous chromosomes are a pair of chromosomes, one obtained
from each parent. They are similar but not identical
Tetrad & Crossing over
•It is the shortest phase
•The tetrads align on the
•Spindle fibers attach to the
kinetochores of the
• Homologous chromosomes
separate and move towards
• Sister chromatids remain
attached at their centromeres.
• Each pole now has haploid
set of chromosomes.
• Cytokinesis occurs and two
haploid daughter cells are
*Cytokinesis is the physical process of cell division
in which the nucleus & cytoplasm divide giving
rise to 2 cells
• In meiosis II, the chromosome number doesn’t
change when compared to meiosis 1 products
• Hence, Meiosis II is similar to mitosis
• Meiosis II consists of 4 stages: Prophase II,
Metaphase II, Anaphase II & Telophase II
• Same as prophase in mitosis
• Chromatin get condensed to
• The spindle fibers are formed
• The centrosomes begin to move
towards either of the poles
• Same as metaphase in Mitosis
• The chromosomes align
themselves on the metaphase
• The spindle fibers attach to the
kinetochores on the centromeres
• Same as anaphase in Mitosis
• Homologous chromosomes do
• Sister chromatids separate
• Each chromosome is thus
broken down into sister
chromatids which move towards
either of the poles
• Same as telophase in Mitosis
• Nuclei are formed.
• Cytokinesis occurs.
• 4 haploid daughter cells produced.
These cells are called as gametes