DNA REPLICATION: MITOSIS &
MEIOSIS
3A3B Biology
DNA REPLICATION
Keywords
Mitosis
 Meiosis
 DNA replication
 Interphase
 Prophase
 Metaphase
 Anaphase
 Telophase
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Keywords
Chromatin
 Chromatids
 Chromosomes
 Centromere
 Centriole
 Spindle fibres
 Cytokinesis
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GENETIC INFORMATION
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Each species has a specific
number of chromosomes,
composed of a particular kind
of DNA
Example:  Humans have 46
chromosomes
 Dogs have 78 chromosomes
 Dandelions have 16
chromosomes
 Strawberries have 14
chromosomes
MITOSIS
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Cell division is responsible
for growth, replacement
and repair.
The activities of a cell are
controlled by the nucleus
Mitosis is the division of
the nucleus.
This process ensures that
genetic information is
accurately copied and
passed on
The result of mitosis is the
formation of two
genetically identical cells –
the parent cell divides to
form 2 identical daughter
cells
STAGES OF MITOSIS
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1.
2.
3.
4.
5.
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Mitosis can be divided
into 5 stages:
Interphase
Prophase
Metaphase
Anaphase
Telophase
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Interphase is a period
when the cell functions
as normal, but is also
preparing for cell
division.
The chromosomes are
strung out in long
chromatin threads
within the nucleus.
Each chromatin thread
is replicated over a
period of time.
All the various
organelles are also being
replicated at this time.
PROPHASE
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Centrioles become
visible in the cytoplasm
Chromatin condenses
into chromosomes
Each chromosome
consists of 2 identical
strands called
chromatids
These are attached to
each other at a point
call the centromere
Nuclear membrane
disappears
centrioles
chromosome –
consisting of 2
chromatids
6
METAPHASE
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spindle fibres
During metaphase the
chromatids line up at
the equator of the cell.
The centromere of each
pair is attached to a
spindle fibre
chromosomes – spindle fibre
attached at the centromere
centrioles
7
ANAPHASE
During anaphase each
pair of chromatids
separate at the
centromere
 The chromatids are
pulled apart towards
the opposite poles of
the cell by the spindle
fibres

spindle fibre
chromatid
centriole
8
TELOPHASE
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During telophase the 2 sets
of chromosomes form tight
groups at each pole
The spindle disappears
Nuclear membranes and
nuclei form
Centrioles divide
Chromosomes uncoil and
disappear
Cytokinesis occurs during
this phase
Cytokinesis is the division
of the cytoplasm
https://www.youtube.com/w
atch?v=P4KCaGkh8v0
centriole
cytokinesis
group of
chromosomes
9
STAGES OF MITOSIS
MEIOSIS
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There is another form of
cell division called
meiosis
Meiosis does not
produce identical
daughter cells that are
copies of the original
parent cell
Instead, cell division
involving meiosis
produces the gametes
(sex cells)
After meiosis, each
gamete ends up with
only half the number of
chromosomes
MEIOSIS
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The process of meiosis
involves two nuclear
divisions, but the
chromosomes
duplicate only once
The first division of
meiosis is similar to
mitosis but during
metaphase I the
chromosomes pair off,
rather than all of them
lining up singly.
The members of each
pair of chromosomes are
identical in size and
shape and are called
homologous pairs
Meiosis
Mitosis
Metaphase I
Metaphase
Homologous
pair of
chromosomes
Metaphase II
MEIOSIS – WHAT HAPPENS IN THE NUCLEUS
Crossing over occurs
during the first prophase.
This ensures genetic
diversity in offspring.
MEIOSIS I & MEIOSIS II
DIPLOID VS HAPLOID CELLS
Term
Definition
Diploid
The number of chromosomes present in the body
(or somatic) cells of an individual (2n)
Haploid
The number of chromosomes present in the
gametes (n)
Mitosis (Amoeba Sisters) 8 min
 https://www.youtube.com/watch?v=gwcwSZIfKlM
Meiosis (Amoeba Sisters) 8 min
https://www.youtube.com/watch?v=toWK0fIyFlY