Figure 1
 1-Mitosis
 2-Meiosis

Mitosis is a kind of cell divison which occurs in
somatic cells and results in two daughter cells.

These daughter cells are identical to each other
and to the parent cell.

Daughter cells are diploid which means that they
they have 2 sets of chromosomes.

One set of chromosomes is donated from the
mother and the other set of chromosome
donated from father.

1-Interphase

2-Prophase

3-Metaphase

4-Anaphase

5-Telophase
Figure 2

There are 3 stages in
interphase;

-G1: The cells grow and
get bigger for the
division.

-S : DNA is synthesized by
the process of DNA
Replication.

-G2 : Mitochondria and
other organelles divide.
Figure 3

Chromosomes become
shorter and fatter.

They move to opposite
poles of the cell and
spindle fibres are
formed.

Nucleolus disappears.

Nuclear membrane
breaks down
Figure 4

Chromosomes line up at
the equator individually.

Spindle fibers attach to
chromosomes at the
centromere.
Figure 5

Spindle fibres pull
chromosomes apart.

Microtubules shortening.

Centromere of each
chromosomes breaks
down.

Daughter chromosomes
travels to opposite poles.
Figure 6

All chromosomes are at
opposite poles.

Spindle fibres break
down.

Nuclear envelope
reformed.

Chromosomes become
invisible.
Figure 7

Meiosis is a kind of cell division which occurs in
gametes(sperms and eggs) and results in four
daughter cells.

Daughter cells are genetically different from each
other and from parent cells.

Daughter cells are haploid which means that they
have one complete set of chromosomes.

During meiosis DNA replicates once but the
nucleus divides twice. Therefore two division occur
in meiosis.

It halves the chromosome number.

It is important to have a diploid cell
with correct number of
chromosome(46 chromosome).

It increases variation.

Prophase 1

Metaphase 1

Anaphase 1

Telophase 1

Most of the steps are
same as in the mitosis
except;

Homologous
chromosomes pair up to
from bivalent consisting
of 4 chromatids.

Two chromosomes can
overlap with each other
which is known as
CROSSING OVER.

Most of the steps are same
as mitosis except;

Spindle fibres move
bivalent chromosomes to
line up at the equator
instead of single
chromosomes.

The centromeres do not
divide

One chromosome from each
homologous pair moves to
each end of the cell.

As a result, the chromosome
number in each cell is half of
the original.

All of the steps are same
as mitosis except;

Whole chromosome is
produced instead of one
sister chromatid.

The second division of meiosis is
completely the same as mitosis.

However at the end of Meiosis, 4
daughter cells each with half of the
chromosome number of the original
diploid cell are formed.
Prophase 2
Metaphase 2
Telophase 2
Anaphase 2

5 differences between mitosis and
meiosis
MITOSIS
MEIOSIS
2 daughter cells formed
4 daughter cells formed
Occurs in body cells
Occurs in gametes
Daughter cells are diploid
Daughter cells are haploid
Daughter cells are identical to
each other
Daughter cells are different from
each other
No crossing over of
chromosomes
Crossing over of chromosomes in
prophase 1
(a) (i) The diagrams show some of the stages of mitosis. Arrange the
letters A - D to give the correct sequence of stages.
Sequence
D
A C
B
(ii)
Describe the role of the spindle in mitosis:
It attaches centromeres and seperates the daughter chromatids.
(b)
Sexual reproduction involves the fusion of gametes. Explain
the importance of meiosis in the life cycle of a sexually reproducing
organism.
Meiosis halves the chromosome number and increase the variation.

Edexcel AS Biology, A Pearson
Company, 2008, page
148,149,150,158,159

Richard Llopis Garcia’s CD