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Cell division
How one cell becomes two
Mitosis + Cytokinesis = Cell division
• Most cells in all eukaryotic organisms will divide
many times throughout the life of the organism
– _______________ is the process by which a cell
duplicates its genetic materials (chromosomes and
prepares for cell division
– ________________ is the division of the rest of the
cell into two separate but identical daughter cells
– __________________________________________
• In animals, cell division occurs during embryonic
development, growth, and wound healing
• Errors during cell division can cause cell death
or cancer
Mitosis reorganizes DNA in the cell
• ______________________________________
• During mitosis, the two copies are reorganized,
repackaged into two sets of chromosomes, and
divided to opposite ends of the cell
• In most organisms,
_(the cell body dividing in two)
• The original cell (mother cell) is identical to the
two resulting cells (daughter cells)
Mitosis vocabulary
Nucleus – location of DNA inside the cell
Nuclear envelope – the membrane that separates the nucleus from the cytoplasm
DNA – an incredibly long molecule that contains genetic blue prints for cell behavior
Chromatin – a loosely bundled coil of DNA. Most of the time, DNA is organized in
this form, “ a loose rope”
Histones – proteins which hold a DNA strand together in the form of chromatin
Chromosome – a highly organized form of chromatin, “a tightly wrapped and carefully
knotted rope ”
Each chromosome is composed of two identical parts called chromatids
Chromatids: two halves of a chromosome which contain the same genetic information
DNA exists in the form of chromosomes only during mitosis
Each chromosome looks like an X
Centromere – a bundle of proteins which connects the two chromatids of a
chromosome, the “knot at the center of the X“
Microtubules – part of a cell’s cytoskeleton. These are tubes of protein which use to
pull chromosomes apart and to opposite ends of a cell during mitosis. They are
powered by ATP!
Mitotic spindle – How microtubules are organized during mitosis. This is a collection
of microtubule fibers which is formed to coordinate the pulling of apart of
Metaphase plate – the line along which chromosomes are lined up during mitosis.
This arrangement is coordinated by the mitotic spindle.
Chromosome Structure
5 Phases of Mitosis
• Mitosis is composed of five phases
• During each phase, different proteins in the cell
perform specific roles to divide the two copies of
genetic material
• _________________________________________
• ________________________
into chromosomes inside the
• Microtubules are organized
in the cytoplasm
• Nuclear envelope is dissolving
• By the end of prophase
– Chromosomes and mitotic
spindle are fully organized
– Nuclear envelope has
• Chromosomes move
towards each other and
into the center of the cell
• Microtubules move into
the nuclear region and
begin to connect to
• ____________________
• The mitotic spindle is fully
organized, and has pulling the
chromosomes to the center of
the cell
• The spindle aligns
chromosomes so that each
centromere is lined up along
the metaphase plate (the
center of the cell)
• _______________________
• Microtubule fibers contract
pulling chromatids to opposite
ends of the cell towards the
two spindles
• _________________________
• New nuclear envelopes begin
to form around the chromatin to
create two nuclei
• Spindle fibers disperse into the
• The cell membrane begins to
cleave in preparation for
• The cell membrane is being pinched off to
form two separate compartments
• Cytoplasm and organelles are being
divided between the two forming cells
• __________________________________
• Cell division is complete!
Cell division movies
• Embryonic division in the worm c.elegans: