3.CELL DIVISION:
MITOSIS
Grade 10
Life Science
Miss L Klein
Terminology
1.Benign
3.Centromere
5.Chromosome
7.Chromatids
9.Malignant
11.Tumour
2.Cancer
4.Cell cycle
6.Cytokinesis
8.Karyokinesis
10.Mitosis
Importance of Mitosis
◦Growth: new cells are formed for growth
◦ Reproduction: allows unicellular organisms
to produce asexually
◦Repair: replaces and repairs damaged cells
The cell cycle
◦The cell cycle starts when the cell forms and ends when
the cell matures and division takes place.
◦The cell cycle has three parts.
1.Interphase: cell growth
2.Mitosis: cell division
3.Cytokinesis: cytoplasm divides into two parts at the end of
cell division.
Mitosis
◦It is the process of cell division where a parent cell
divides into 2 daughter cells
◦Two division processes are important in mitosis:
◦Karyokinesis and cytokinesis
Mitosis has four phases.
1. PROPHASE
2. METAPHASE
3. ANAPHASE
4. TELOPHASE
◦Before the cell divides, all the DNA is
replicated (DNA replication)
◦Once DNA replication takes place, each
chromosome appears as two chromatids,
which are held together by a centromere.
1. Prophase
◦Chromosomes coil up
◦Nuclear envelope
disappears
◦Spindle fibres form
2. Metaphase
◦Chromosomes line up
in middle of cell
◦Spindle fibres connect
to chromosomes
3. Anaphase
◦Chromosome copies
divide
◦Spindle fibres pull
chromosomes to
opposite poles
4. Telophase
◦Chromosomes uncoil
◦Nuclear envelopes
form
◦2 new nuclei are
formed
◦Spindle fibres disappear
Cytokinesis
◦It is the division of the rest of the cell (cytoplasm
and organelles) after the nucleus divides
◦In animal cells the cytoplasm pinches in
◦In plant cells a cell plate is formed
◦After mitosis and cytokinesis the cell returns to
Interphase to continue to grow and perform
regular cell ativities.
UNCONTROLLED
CELL DIVISION
(CANCER)
◦The cell cycle is controlled by signals and the body cells
divide between 20 to 50 times, then get old and die.
◦However, some cells ignore the signals and carry on
dividing to form a mass of cells which become
cancerous.
◦They cause different cancers depending on where they
are.
◦Cancer is dangerous because it can spread and attack
healthy organs
Different Kinds of Cancers
◦1. Carcinomas: skin or epithelium cancer
lining organs, glands and skin
◦2. Sarcomas: bone, cartilage and muscle
◦3. Leukaemia: blood and lymphatic and
immune system
Causes of Cancer
◦Cancer is uncontrolled cell growth.
◦Different types are caused by different factors called carcinogens.
◦These could be:
◦ Inherited
◦ Smoking
◦ Processed foods
◦ Viruses
-Radiation
-Hormonal imbalances
-Pollutants and pesticides
Two Types of Tumours
◦Benign tumour: cell masses that stay at one site;
does not spread
◦Malignant tumour: cancerous cells can leave the
first site and invade other organs and tissue in a
process called metastasis.
Treatment of Cancer
1.Surgery:
2.Chemotherapy
3.Radiation