1. CHAPTER 3
HEREDITY AND VARIATION

2. 3.1 CELL DIVISION
•Human beings have 46 chromosomes.
•Chromosomes are located in the nucleus.
•Chromosomes consists of DNA and
proteins.
•Gene carry genetic information's.

3. CELL DIVISION (PEMBAHAGIAN SEL)

There are two types of cell division:
Cell division
Mitosis
Meiosis
* Somatic cell (other than
reproductive cell)
* Produces 2 daughter cells
* Reproductive cell (sperm
and ovum)
* Produces 4 daughter cells

4. MITOSIS
Chromosome
shorten and
thicken
•Replication of
chromosome
•Chromosomes align at
the centre of the cell
•The nucleus membrane
disappears
•Chromatids separate
and move to the
opposite
•The cell starts to divide
•The nucleus membrane
forms.
•2 daughter cells
•Same number of
chromosomes

5. MITOSIS UNDER
MICROSCOPE

6. IMPORTANCE OF MITOSIS
Produce new cells for growth and to replace
damaged cells
 Ensures the number of chromosomes in the
daughter cell is the same as that of the parent cell


7. MEIOSIS
Replication
and crossing
over
•Half number of
chromosomes
Produces
4 daughter
cells

8. MEIOSIS UNDER MICROSCOPE

9. IMPORTANCE OF MEIOSIS
To produce gametes/reproductive cells (sperm or
ovum)
 Allows for genetic variations among the same
species
