2. LEARNING OUTCOMES
• To state the necessity of trait inheritance in
offspring for continuation of life,
• To state the necessity to maintain diploid
chromosomal number from generation to
generation,
• To state the necessity for production of haploid
gametes in sexual reproduction,
• To state the significance of meiosis,
• To identify the type of cell that undergoes meiosis,
• To explain the process of meiosis,
• To arrange the various stages of meiosis in the
correct order,
• To compare and contrast meiosis I & meiosis II,
• To compare and contrast meiosis & mitosis.

3. M E IO S IS
• A division of the nucleus to produce 4 daughter
cells each containing half the chromosome number
of the parent nucleus.
• A type of cell division - occurs in reproduction
organs to produce 4 daughter cells called gametes.
• The process of nuclear division that reduces the
number of chromosomes in new cells to half the
number of chromosomes in the parent cell.
• Each daughter cell receives 1 set of chromosome
from each pair of homologous chromosomes –
haploid cell (n)

4. MEIOSIS
• Genetic material in the gametes differs from
the parent cell & each other
• Animals : testes in males – sperm
ovaries in females – ovum
• Plants : anthers – pollen (male gametes)
ovaries – ovules (egg cells)
• Consists of Meiosis I and Meiosis II

5. THE SIGNIFICANCE OF
MEIOSIS
• To allow trait inheritance in offspring
– the transmission of traits
• To maintain diploid number in each
generation - the organisms are always diploid
• To ensure the production of haploid
gametes in sexual reproduction
• To produce genetic variation among
offsprings

6. M E IO S IS
• Meiosis I : the homologous chromosomes are
separated into two haploid daughter cells
• Meiosis II : the sister chromatids of each
daughter cell are separated.
• Meiosis II = mitosis in a haploid cell
• All chromosomes are replicated during
interphase  sister chromatids joined at
centromere. The chromosomes do not
replicate again between Meiosis I & Meiosis II

7. MEIOSIS I
PROPHASE I
• Centrioles move to opposite poles.
• Chromosomes thicken & condense
• The homologous chromosomes form bivalent
through synapsis
• Crossing over happened : non-sister
chromatids exchange segments of DNA  new
combination of genes on a chromosome
• Chiasmata – the points at which segments of
chromatids cross over
• Nucleus membrane & nucleolus disappear
• Spindle fibres are formed

8. M E TA P H A S E I
• The paired chromosomes are lined
up at the equator of the cell
• One chromosome of each pair faces
each pole of the cell
• the chromosomes attached to the
spindle fibres at their centromere
• The centromere does not divide

9. ANAPHASE I
• The paired chromosomes separate from
one another & move to opposite poles
• The spindle fibres pulled one
chromosome of each pair to each pole

10. TE L O P H A S E I
• The chromosomes arrive at the poles.
• Each pole has a haploid daughter nucleus
(contain one set)
• The spindle fibres disappear, the nuclear
membrane & nucleolus reappears in each
nucleus.
• Cytokinesis occurs
• No interphase, no replication of
chromosomes

11. MEIOSIS II
PROPHASE II
• Centriole duplicates & move
to opposite pole
• Nuclear membrane
disappear, spindle fibres re-
form
• The chromosomes move to
the equator of the spindle.

12. M E T A P H A S E II
• Chromosomes lined up
at the equator of the
cell facing opposite
poles
• Each sister chromatid
is attached to the
spindle fibres at the
centromere

13. ANAPHASE
II
• The sister chromatids
together split
• Chromatids separate
• Spindle fibres pull each
chromatid to opposite poles
• Centromere are divided

14. T E L O P H A S E II
• Chromatids reach the poles &
become new chromosomes
• Nuclear membrane & nucleolus
form again at each
chromosome
• Chromosomes become
extended & not visible
• Cytokinesis occurs & 4 haploid
daughter cell are formed.

16. T H E C O M P A R IS O N B E T W E E N
M E IO S IS I & M E IO S IS II
MEIOSIS I SIMILARITIES MEIOSIS II
•Consist of 4 stages : P,M,A,T
•Involve division of nucleus & cytokinesis
DIFFERENCES
Occur Synapsis Not occur
Yes Cross over No
MI-paired homologous Metaphase MII – each chromosome
chromosomes line up at with sister chromatids
the equator line up at the equator
AI – paired homologous Anaphase AII – the sister
chromosomes separate chromatids separate &
& move to opposite move to opposite poles
poles
2 haploid cells are At the end 4 haploid cells are
formed formed

17. T H E C O M P A R IS O N B E T W E E N M IT O S IS
& M E IO S IS
MEIOSIS SIMILARITIES MITOSIS
•Division of cells
•The chromosomes replicates only once
DIFFERENCES
In reproductive organ Place occur In somatic cell
Parent cell divides twice Number of divisions Parent cell divides once
Four haploid daughter cells Number of daughter cells Two diploid daughter cells
Occurs during prophase I Synapsis of homologous Not occurs
chromosomes
Occurs twice Number of cytokinesis Occurs once
Occurs during prophase I Crossing over of chromatids of Not occurs
homologous chromosomes
Half of number of chromosomes Number of chromosomes in Genetically identical to the parent
of the parent cell (haploid) daughter cells cell
Genetically non-identical to the Genetic composition of Genetically identical to the parent
parent cell & each other daughter cells cell
Occurs once during interphase DNA replication Occurs during interphase before
before meiosis I mitosis begins