stages of meiosis

2. TOPIC : MEIOSIS

3. MEIOSIS
 Meiosis is the mode of cell division in
which gametes are formed.
 Meiosis occurs in the germinal cells of
the reproductive organs.
 Human beings have 46 chromosomes.
 Germinal cells with 46 chromosomes
divide continuously two times.
 These divisions in meiosis are known
as Meiosis 1 and Meiosis 2.

4. MEIOSIS 1 and 2
 Two daughter cells with half the number of
chromosomes (23 chromosomes) are formed in
meiosis 1.
 Each daughter cell again divides in meiosis 2.
 There is no change in the chromosome number n
this division.
 Meiosis 2 is similar to mitosis.
 As a result of meiosis, four daughter cells, each
with 23 chromosomes, are formed from a
germinal cell.

5. STAGES OF GAMETOGENESIS

6. POLAR BODY
 When meiosis occurs in the female
germinal cell, a large ovum and three
small cells are formed.
 The smaller cells are the polar bodies.
 These sterile cells get destroyed.

7. DIFFERENCE BETWEEN MITOSIS AND MEIOSIS
MITOSIS MEIOSIS
In which kind of cell does it
takes place?
Body cells Stoma tic cells
The change in the number
of chromosome.
Same as that of the
parent nucleus
Half of the parent
nucleus
Number of daughter cells Two Four

8. STAGES OF GROWTH OF HUMAN BEING
 INFANCY
 CHILD HOOD
 ADOLESCENCE
 OLDAGE

9. PHYSICAL PECULARITIES OF OLDAGE
 Rate of cell division decreases.
 Availability of oxygen to the cells
decreases.
 Deterioration of cells increase.
 Muscles shrink.
 Production of energy decreases.
 Efficiency of sense organs decreases.

10. QUESTIONS
1. What is meiosis?
2. What is the number of chromosomes in
germinal cells?
3. What is the number of chromosomes in the
daughter cells formed after meiosis 1 ?
4. What is the peculiarity of meiosis 2 ?
5. What is polar bodies?

11. HOME WORK
 Write the differences between mitosis and
meiosis?
 Draw the stages of gametogenesis in your
science diary?