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Mitosis
Mitosis
BIOLOGY 1
TURNER COLLEGE & CAREER HIGH SCHOOL
Mitosis is the process in which the
nucleus divides to form two new
nuclei.
How does mitosis differ in plants and animals?
How do little elephants grow
up to be BIG elephants?
Why do animals shed their
skin?
Three reasons why cells reproduce
by asexual reproduction:
1. Growth
2. Repair
3. Replacement
Skin cancer: the abnormal growth of
skin cells; most often develops on skin
exposed to the sun.
• Cell that reproduce by asexual
reproduction reproduce constantly.
Mitosis Cycle
• Interphase
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokinesis
Interphase:
Occurs Before Mitosis Begins
• Each stage of interphase has a distinct set of
specialized biochemical processes that prepares the
cell for initiation of cell division.
Interphase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
G1 Phase
o Growth and young cell maturation
occurs.
o G1 phase is the phase during which
the cell cycle starts with the
production of RNA and proteins
required by the young cells for their
growth and maturity.
o The time period of the G1 phase of
the interphase varies highly among
the different species of eukaryotic
cells.
o Chromosomes begin to condense.
S Phase
o All of the chromosomes are
copied.
o Chromosomes appear as
threadlike coils (chromatin) at
the start, but each chromosome
and its copy change to sister
chromatids at end of this phase.
o Following replication, each
chromosome now consists of
two sister chromatids.
G2 Phase
o During G2, the cell
synthesizes a variety of
proteins.
o Of particular significance
to the cell cycle, most
microtubules – proteins
that are required during
mitosis – are produced
during G2.
Mitosis
• Prophase
• Metaphase
• Anaphase
• Telophase
1: Prophase
o Chromosomes become more coiled and can be viewed
under a light microscope.
o Each duplicated chromosome is seen as a pair of sister
chromatids joined by the duplicated but unseparated
centromere.
o The nucleolus disappears during prophase.
o In the cytoplasm, the mitotic spindle, consisting of
microtubules and other proteins, forms between the two
pairs of centrioles as they migrate to opposite poles of the
cell.
o The nuclear envelope disappears at the end of
prophase.
1: Prophase
Prophase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
2: Metaphase
o The centrosomes are at opposite poles of the cell.
o The chromosomes, now at their most highly coiled
and condensed, become arranged on a plane
equidistant from the two poles called the metaphase
plate (or equator).
o For each chromosome, the kinetochores of the
sister chromatids face the opposite poles, and each is
attached to a kinetochore microtubule coming from
that pole.
2: Metaphase
Metaphase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
3: Anaphase
o Begins when the duplicated centromeres of each
pair of sister chromatids separate, and the nowdaughter chromosomes begin moving toward
opposite poles of the cell due to the action of the
spindle.
o Depending where the centromere is located along the
chromosome, a characteristic shape appears during
chromosome movement.
o At the end of anaphase, a complete set of
chromosomes has assembled at each pole of the cell.
3: Anaphase
Anaphase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
4: Telophase
o The chromosomes assemble in sets at the two poles.
o The chromosomes begin to uncoil and eventually
assume the extended state characteristic of
interphase.
o A nuclear envelope reforms around each chromosome
set, the spindle disappears, and the nucleolus
reforms.
o Nuclear division by mitosis is complete at this point.
4: Telophase
Telophase
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Cytokinesis
Cytokinesis, the division of the cytoplasm, usually is in
progress before nuclear division is complete.
◦ In animal cells, cytokinesis involves the formation of a cleavage
furrow resulting in the pinching of the cell into two.
◦ In plant cells, cytokinesis involves the formation of the cell
plate resulting in formation of the cell wall, creating two cells.
Cytokinesis
Animal Mitosis: Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Plant Mitosis: Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
REMEMBER!
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Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
I Picked More Apples Today Carefully.