2. CONCEPT OF MITOSIS
Plants and animals are known to undergo sexual reproduction.
Sexual reproduction results in the formation of single cells called
Zygotes.
This zygote is made up of million of cells and must develop.
Therefore these single cells must divide many times in order for the
zygote to grow and develop into an adult.
This type of cell division that takes place is known as Mitosis.
Mitosis can therefore be defined as a process where by one cell
divides to form two cells that are identical to each other and the
parent cell which the two cells come from
Therefor only body or sometic cells undergo mitosis.(somatic cells
are all cell other than sex cell)
3. CHROMOSOMES
Chromosomes are formed when the chromatin network, which is
situated in the nucleus, coils up, thickens and shorten.
Chromosomes are known to be made up of DNA,
and DNA contains the genetic code for controlling the appearance
and function of thousands of cells.
Different organisms are known to have different number of
chromosomes.
Humans therefore have 46 chromosomes (23 pairs)
They are also arranged in identical pairs.
One chromosome consist of 2 chromatids and only one centromere
that attach the two chromatids together.
Chromosomes are known to be visible only during cell division.
5. WHY IS MITOSIS IMPORTANT?
Reproduction in some simple organisms.
Repairing of damaged cells/tissues.
Replacing of dead cells/tissues.
Mitosis allows organisms to grow.
6. THE CELL CYCLE
Mitosis refers to the division of the nucleus only
into two nuclei, therefore interphase and
cytokinesis are not part of the process of mitosis.
The cell cycle is therefore:
Interphase(this includes G1,S-[DNA synthesis] and
G2phase.
Mitosis.
Cytokinesis
Growth
This results in the formation of two identical cells.
7. THE PROCESS OF MITOSIS
Consist of the following phases:
Interphase
Prophase
Metaphase
Anaphase
Telophase
8. INTERPHASE
• In this phase, the cell prepares for cell division
,this is by building up enough energy.
• The DNA replicates(doubles) itself, so that the
genetic material is double.
9. PROPHASE
The nuclear envelop and nucleolus disappears.
The chromatin network becomes tight and then coils
up and is now visible as chromosomes.
Chromosomes now arrange randomly within the cell
Centrioles move to the opposite ends with spindle
fibres between them.
10. METAPHASE
The chromosomes arrange themselves randomly
along the equator of the cell, each are attached to a
spindle fibre.
The centriole have now finally reached the opposite
poles, attached to the chromosomes by means of a
spindle fibres to the centromere.
11. ANAPHASE
• Spindle fibres now pulls tight , thus splitting the
chromosomes into two chromatids splits into two.
• The centromere that attaches the two chromatids
also splits into two.
• The two daughter chromosomes then move to the
opposite poles
12. TELOPHASE
• Now two groups of chromosomes occur, the occur at
opposite ends.
• The nucleus envelop now surrounds the
chromosomes at the opposite poles.
• Nucleolus now reappears at each poles.
• The chromosomes now become less dense and now
are visible as chromatin network
13. LATE TELOPHASE
• Invagination of the cytoplasm and the plasma
occurs.
• This then goes on until the cell has totally
divided into two separate identical cells.