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Monday, 22 May 2017
Mitosis
Learning Objectives:
1. State why cells divide
2. Describe the advantages of being multicellular
3. Explain how cells divide by mitosis
Starter
Why do you need to make new cells?
Why do you need new cells
Skin cells are continually lost. To make
new cells the body carries out cell
division
Cells divide where the body needs to:
• Grow
• Replace worn out cells
• Repair damaged tissue
Difference between…
Uni-cellular
And
Multi-cellular
Differentiation…recap
Differentiation: Cells become different
shapes of sizes to carry out specialised
jobs
Advantages of being multi-cellular
• Can grow larger
• Differentiation means cells become
specialised to perform different
functions
• Become more complex eg develop organ
systems.
Chromosomes recap
• Every cell contains 46 pairs of
chromosomes.
• These pairs are said to be homologous
• A cell that has pairs of chromosomes is
said to be diploid
Keywords
• Spindle- Structure in cells that
separates the chromosomes during cell
division.
• Diploid- Full set of chromosomes (46)
• Haploid- Half set of chromosomes (23)
e.g. Sperm cell.
Mitosis
• The name for making new cells. The new
cells are genetically identical to the
original cell
Stages of mitosis
•Spindle
•Chromosome
forms.
single
Chromosomes
strands
move
arranged
to the
•Each
chromosome
is
copied
(DNA
••Two
Cell genetically
resting
identical cells are produced
along the
poles
of the
equator
cell
replication)
Mitosis. Mitosis. What every cell knows is…
it happens all the time.
Cells undergoing mitosis
• A cell has 2
versions of
each
chromosome –
one from each
parent.
• We call this
type of cell
diploid.
• To prepare for
cell division,
each
chromosome is
copied.
• The chromosomes
line up in the
centre of the cell.
The two copies of each
chromosome are
pulled apart by
spindle fibers.
• The chromosomes
move to different
sides of the cell.
• Cytoplasm
Divides.
• The cell begins to
split in two.
• The cell completely
splits in two.
• There are now two
cells, these are
called daughter cells
(both diploid).
• Each cell is
genetically identical
to each other, and to
the original parent
cell.
Asexual Reproduction
• Some organisms reproduce by
mitosis. E.g. Strawberry plants form
runners in this way which become new
plants.
• This is an example of asexual
reproduction.
• The offspring have exactly the same
genes as the parent- therefore......
Where does mitosis happen?
• Most of the cells in the body
divide by mitosis.
• Can you think of any
exceptions?
• Some organisms can
reproduce by mitosis. This is
called asexual reproduction.
• Examples include yeast and
the malaria parasite.
Cancer and Mitosis?
Is there any link?
What happens when mitosis goes
wrong?
• Usually cells only
divide at certain
times.
• Sometimes this
control stops working
and cells divide
uncontrollably – this
is cancer.
•
•
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•
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What is mitosis?
Why is mitosis important?
What would happen if mitosis didn’t take place?
Suggest one advantage and one disadvantage of
asexual reproduction.
What is meant by a diploid cell?
What cells in the body do you think are not
diploid?
How many parents does a cell that reproduces
by sexual reproduction have?
How many parents does a cell that reproduces
by asexual reproduction have?
Can you give an example of what happens when
mitosis goes wrong?