Mitosis Revision Sheets

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Mitosis Cytokinesis
Mitosis is a type of cell division that produces genetically identical cells. During mitosis DNA
replicates in the parent cell, which divides into two new cells, each containing an exact copy of
the DNA in the parent cell. The only source of genetic variation in the cells is via mutations.
This is when the cell is not dividing, but is carrying out
its normal cellular functions.
chromatin not visible
Interphase
DNA, histones and centrioles all replicated
Replication of cell organelles e.g. mitochondria,
occurs in the cytoplasm.
chromosomes condense and become visible ­ this
prevents tangling with other chromosomes.
Due to DNA replication during interphase, each
chromosome consists of two identical sister
Prophase chromatids connected at the centromere
centrioles move to opposite poles of cell
nucleolus disappears
phase ends with the breakdown of the nuclear
membrane
spindle fibres (microtubules) connect centrioles to
chromosomes
Metaphase
chromosomes align along equator of cell and attaches
to a spindle fibre by its centromere.
centromeres split, allowing chromatids to separate
chromatids move towards poles, centromeres first,
pulled by kinesin (motor) proteins walking along
Anaphase
microtubules (the track)
Numerous mitochondria around the spindle provide
energy for movement

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Telophase
chromatids
nucleoli form
Cytokinesis
In animal cells a ring of actin filaments forms round
the equator of the cell, and then tightens to form a
cleavage furrow, which splits the cell in two.
In plant cells vesicles move to the equator, line up and
fuse to form two membranes called the cell plate. A
new cell wall is laid down between the membranes,
which fuses with the existing cell wall.
Cell Continuity is the unbroken succession of cells since life evolved 3.…read more

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The cytoplasm di
· Therefore each nucleus with its allocation of cytopbecomes a new cell.
s
A· H
chromosome is present.)
· Diploid (2n): two sets of chromosomes are present in the nuclei (i.e. two of each
different chromosome are present.)
le f Mitosis Formation of a multicellula
· Asexual r
· Cell replacement and regeneration.…read more

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Stages of Mitosis (Interphase) Metaphase, Anaphase, Telophase.…read more

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Definitions
Chromatin: DNA in its `normal', i.e. functional state -- condenses to form chromosomes.…read more

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I. Prophase
1. The chromatin condenses into chromosomes by dehydrating and coiling. The
chromosomes consist of two identical sister chromatids, joined together by a centromere.
For the first time, they can be seen with alight microscope.
2. The nucleolus and nuclear envelope disappear, and the centriole (animal cells only) divides
into two centrosomes, which move apart, creating the spindle. This eventually fills the
whole of the cell and is made of the protein tubulin which forms spindle fibres ­ a form of
microtubule.
II.…read more

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Chromosomes can be grouped into homologous pairs
Mitosis occurs in
o Growth
o Repair
o Replacement of cells with limiting life span (red blood, skin cells)
o Asexual replacement
Controlled process, cancers result from uncontrolled mitosis of abnormal cells
Division of the nucleus (karyokinesis) and the cytoplasm (cytokinesis) are two
processes of mitosis
Division of cytoplasm after nucleus. Delayed if cells have more than one nucleus
(muscle)
Active process that requires ATP
Prophase
1.…read more

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