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Gr:10
CELLS DIVISION: MITOSIS
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INTRODUCTION
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THE CELL CYCLE is the series of events that takes place in a cell that results in DNA replication and cell division
There are two main stages in the cell cycle.
1. interphase during which the cell grows and replicates its DNA.
2. mitotic phase (M-Phase) during which the cell divides and transfers one copy of its DNA to two identical daughter cells
THE SEQUENCE OF EVENTS
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Interphase: DNA in chromatin network duplicates.
DNA thickens and becomes visible.
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MITOSIS Purpose and location of mitosis
Growth – multicellular organisms need cell division to grow
Repair – organisms constantly repair and renew themselves; worn out or dead cells are replaced through cell division.
Reproduction – single-celled organisms, such as bacteria and protists, also reproduce by cell division (binary fission and budding).
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MITOSIS OCCURS In plants
apical meristem tissues behind the tip of the root or stem and in buds
lateral meristem tissues underneath bark.
In animals
bone marrow
skin basal layers. BY: M.SAIDI for help +27848331738
Chromosome structure:
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(1) Chromatid,
(2) Short and
(3) Centromere,
(4) Long arms of chromosome.
PHASES OF MITOSIS NOTE:
Mitosis Results: a mature cell divides into two identical new cells.
karyokinesis – division of the nucleus
cytokinesis – division of the cytoplasm
PHASES INCLUDE 1. prophase
2. metaphase
3. anaphase
4. telophase
. cytokinesis
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iPMATc.
1. PROPHASE the nuclear membrane and nucleolus disintegrates
A centrosome forms centrioles.
centrioles separate and move to opposite poles
The centrioles give rise to the spindle fibres which form between the poles.
Each chromosome is visible as two chromatids joined by a centromere
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2. METAPHASE chromosomes line up on the equator of
the cell.
Each chromosome is attached to the spindle fibres by its centromere.
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3. ANAPHASE Each chromosome separates into its sister
chromatids by the action of spindle fibres pulling each towards a spindle pole.
Each chromatid is pulled to opposite poles of the cell
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4. TELOPHASE a nuclear membrane reforms around the
daughter chromosomes that have gathered at each of the poles.
The daughter chromosomes uncoil to form chromatin once again.
The nuclear membrane reforms.
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CYTOKINESIS is the division of the cytoplasm
Its not a stage of mitosis but the process of the cytoplasm splitting into two.
In an animal cell the cell membrane constricts
In a plant cell a cross wall is formed by the cell plate dividing the cytoplasm in two.
There are now two genetically identical daughter cells which are identical to the parent cell and to each other.
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DIFFERENCES BETWEEN MITOSIS IN ANIMAL CELL AND PLANT CELL
ANIMAL CELL PLANT CELL
occurs throughout the body occurs in the meristem eg tip of root
Cytokinesis occurs by cleavage in animal mitosis
Cytokinesis occurs through the formation of a cell plate in plant mitosis
Centrosomes / sindle form Centrosomes /sindle don’t form
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Living Process Role of Mitosis
Development and growth
The number of cells increases by mitosis
enabling organisms to grow from a single
cell to a complex multicellular organism.
Cell replacement
Cells are constantly lost and replaced by
new ones in the body, for example in the
skin and in the gut, red blood cells live for
only four months, and are replaced by
mitosis.
Replacement of damaged plant or
animal tissue (regeneration)
Some organisms use mitosis to replace
body parts. For example starfish replace
lost arms by mitosis.
Asexual reproduction
Some organisms such as the hydra use
mitosis to produce genetically identical
offspring. The process is known as
budding. Mitosis is also the method by
which yeast cells multiply. BY: M.SAIDI for help +27848331738
ROLE OF MITOSIS
Reproduction in some simple organisms
Asexual reproduction uses mitosis.
Eg in ciliated organism
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Undergoing cytokinesis
CANCER is uncontrolled cell division and growth (mitosis), causing a
tumour to develop.
KINDS OF CANCER CELLS Benign tumours are cancerous cells found at the original site
that do not move through the body. are non-cancerous.
Malignant tumours leave the original site and move throughout the body invading other organs and tissues
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TYPES OF CANCER Breast cancer
Lung cancer
Oesophageal cancer
Leukaemia (blood cancer)
Melanoma (skin cancer)
sarcomas – bone, cartilage and muscle
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CAUSES OF CANCER Cancer is caused by different factors called
carcinogens.
Carcinogens are:
inherited susceptibility
radiation (sun, X-rays, radioactivity)
smoking
hormonal imbalances
processed foods
pollutants
pesticides
viruses. BY: M.SAIDI for help +27848331738
Beliefs and attitudes about cancer It is people's fault if they get cancer
Cancer is a death sentence
If someone in your family has cancer you might get it too
Cancer is contagious and you can catch it from others
A positive attitude can cure cancer
Only old people get cancer
Only females get breast cancer
Only pale people get skin cancer
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Cancer treatment Medical biotechnology used in cancer treatment is:
Surgery – to cut it out with a scalpel or laser
Chemotherapy – chemical compounds kill the cancer cells
Radiotherapy – can use machines, radiation, injections of compounds and capsules.
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Chemotherapy Radiotherapy
Traditional technology used in cancer treatment includes natural remedies like Cancer Bush tea and African wild potato tea.
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Cancer Bush tea African wild potato tea
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END OF TERM 2
PLANT AND ANIMAL TISSUES
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