Cell Division and Mitosis
1. Cell division functions-___________,_____________
• Cell division requires the distribution of
_________ genetic material (DNA) to two
2. Cell division distributes identical sets
of chromosomes to daughter cells
• A cell’s genetic information, packaged as
DNA, is called its _____________
• In prokaryotes, _______ DNA molecule.
• In eukaryotes,- _____ DNA molecules.
• DNA molecules are packaged into _____________
• Every eukaryotic species has a characteristic number of
chromosomes in the nucleus.
• Human __________ (body cells) have 46 chromosomes.
• Human _______sperm or eggs) have 23 chromosomes,
half the number in a somatic cell.
______ - The process of the formation of the ____
daughter nuclei from a single parental cell
• is usually followed by division of the cytoplasm,
• Result- two cells that are the genetic __________ of
_______ – one parental cell produces __ daughter cells
• Occurs only in the ______(ovaries and testes),
• Result- Each cell has half the chromosomes.
• In humans, meiosis reduces the number of
chromosomes from __to ___
• Fertilization fuses two ______ together and doubles
the number of chromosomes to ___ again.
3. The mitotic phase alternates with
interphase in the cell cycle: an overview
• The ___________ of the
cell cycle alternates with
the much longer
• The M phase includes
____ and __________.
• Interphase accounts
for ____ of the cell
Interphase has three subphases:
•the _______ (“first gap”)
centered on growth
•the _____ (“synthesis”)
when the chromosomes are
•the ______ (“second gap”)
where the cell completes
preparations for cell
Mitosis- 6 phases
Fig. 12.5 left
•Chromosome _________ •Chromosomes coiled
•Mitotic _______ forms
•Microtubles attach to
_________ on centromere
arranged in “_____”
6. ________and ____________
•Chromosomes pulled to
•Nuclei begin forming
4. The ____________ distributes
chromosomes to daughter cells
• The ________________
• fibers composed of _________and
• is a major driving force in __________.
• Assembled during _______from
• The spindle fibers elongate by
incorporating more subunits of the protein
Cytokinesis divides the cytoplasm
• follows ______
• In animals- A contractile
ring of ____
microfilaments and the
motor protein ______
form to pinch the cell in
• In plants- vesicles
from the Golgi coalesce at
the metaphase plate,
forming a _________.
• The plate enlarges until its
5. Prokaryotes reproduce by __________,
• Bacterial genes located on a
• In binary fission, chromosome
replication begins at one point
in the circular chromosome, the
• These copied regions begin to
move to opposite ends of the
• Mechanism is unknown
are unknown in
6. A molecular control system drives the
• The _______ and _____ of cell division varies with
• Skin cells divide often, mature nerve and muscle cells not at all
• The cell cycle is
driven by specific
• Evidence-Fusion of an
M phase and a G1
phase cell, induces the
__ nucleus to start ___
• The distinct events of the cell cycle are directed by
a distinct cell cycle ___________________.
Three major checkpoints are
found in the __-___ , and __
A ___________ - control
point where stop and go
signals regulate the cycle.
If no go-ahead signal, the cell exits
the cycle and switches to a
nondividing state, the ___ phase.
•Most human cells are in the
7. Internal and external cues help ________
the cell cycle
• Growth factors stimulate cells to ________
Example: Platelet-derived growth factors
(PDGF), produced by platelet blood cells,
bind to tyrosine-kinase receptors of
fibroblasts, and triggers a signal-transduction
pathway that leads to cell division.
• The role of _____ is easily seen in cell culture.
• Fibroblasts in culture will only divide in the presence
of medium that also contains PDGF.
• Growth factors appear to be a key in______________________________ of cell division.
• Cultured cells normally
divide until they form a
___________ on the inner
surface of the culture
• If a gap is created, the
cells will grow to fill
Most animal cells also
__________for cell division.
•Must be anchored to a __________, typically the
____________________ of a tissue
8. Cancer cells have escaped from cell cycle
•Cancer cells are free of both 1-____________________ and
• Cancer cells divide excessively and invade other
tissues because they are free of the body’s control
• If and when cancer cells stop dividing, they do so at
random points, not at the ______________ in the cell
• Cancer cell may divide indefinitely if they have a continual
supply of ________________.
• In contrast, nearly all mammalian cells divide _______ times
under culture conditions before they stop, age, and die.
• ________________- a single cell in a tissue
converts to a cancer cell.
• Normally, the immune system recognizes and destroys
• However, cells that evade destruction proliferate to
form a tumor, a mass of abnormal cells.
• ________ tumor- The abnormal cells remain at
the originating site.
• __________ tumor- the abnormal cells leave the
original site to impair the functions of one or more
organs (Known as __________).
• _________- Cancer cells are carried by the blood and
lymph system to new sites and start more tumors.
A typical cancer senario- breast cancer
• Treatments for metastasizing cancers include high-energy
______________ and _____________with toxic drugs.
• These treatments target actively __________cells.