Meiosis is a germ cell division process that results in the formation of gametes and ensures the diploid number of chromosomes is restored during fertilization. It consists of one round of DNA replication followed by two successive cell divisions. In the first meiotic division, homologous chromosomes pair up and separate, reducing the number of chromosomes by half to form two haploid cells. The second meiotic division then separates the chromatids, resulting in four haploid daughter cells each containing a single set of chromosomes. Meiosis produces genetic variation between generations and is essential for sexual reproduction.

1. meiosis
A GERM CELL DIVISION

2. meiosis
 Meiosis ensures production of haploid
phase and fertilization restores diploid
phase
 Interphase has GI and GII phase and s
phase
 Replication of chromosomes takes place
in S PHASE

3. Key features
 It occurs in germ cells and results in the
formation of gametes.
 It results in formation of 4 daughter cells
(each contains 23 schromosomes=haploid number).
 It consists of two successive divisions;
without an intervening S phase.

4. First meiotic division (reductional division)
 It is preceded by interphase with an S phase, in which
the chromosomes are replicated (46 s chromosomes 46
d chromosomes).
 1-Prophase I:
 tetrads form and crossing over occurs, creating new,
recombinant chromosomes.

5. First meiotic division (reductional division)
 2- Metaphase I:
 The paired chromosomes arrange themselves
at the equatorial plate of the cell.
 3- Anaphase I:
 The centromeres do not divide, instead, each
chromosome of homologous pairs moves
separately towards the opposite poles of the
cell.

6. First meiotic division (reductional division)
 4- Telophase I:
 Chromosomes gather at the poles of the
cell. The cytoplasm divides
 Cytokinesis occurs results in two daughter
cells each containing the haploid number(
23dchromosomes).

7. II-Second meiotic division (equatorial division)
 • It is similar to mitosis but, it is not
preceded by S phase.
 • It results in formation of 4 daughter cells,
each contains 23 s-chromosomes (haploid
number).

9. Meiosis I and Meiosis II
 1- Preceded S phase
 2- Prophase
 3- Metaphase
 4- Anaphase
 5- Telophase
46d chromosomes
23d chromosomes 23s chromosomes

10. Significance
 Meiosis is the mechanism by which conservation of specific chromosomes
number of each species is achieved across generations in sexually
reproducing organisms even though paradoxically results in reduction of
chromosomes number by half .
 It also increases the genetic variability in population of organisms from on
generation to the next
 Variations are very important for the process of evolution

11. Thank you for your attention