Transcript Bio1100Ch12W

CHAPTER 12
THE CELL CYCLE
1. Cell division functions- _________________________
and ____________
• Cell division requires the distribution of identical
genetic material - DNA - to two daughter cells.
• A dividing cell _____________ its DNA, allocates
the two copies to opposite ends of the cell, and
then splits into two daughter cells.
Fig. 12.2c
2. Cell division distributes identical sets
of chromosomes to daughter cells
• A cell’s genetic information, packaged as
DNA, is called its _________.
• In prokaryotes, the genome is often a _________
DNA molecule.
• In eukaryotes, the genome consists of
________DNA molecules.
Fig. 2.3
• 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
two daughter nuclei from a single parental cell
• is usually followed by division of the cytoplasm,
_____________.
• Result- two cells that are the genetic equivalent of the
parent.
• _______ – 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
cycle.
Fig. 12.5
Interphase has three subphases:
•the ________ (“first gap”)
centered on growth
•the _________
(“synthesis”) when the
chromosomes are copied
•the _________ (“second
gap”) where the cell
completes preparations for
cell division
Mitosis- 6 phases
1. _________
Fig. 12.6 left
2. _________
•Chromosomes coiled
•Chromosome duplicated •Sister chromatids joined
•Mitotic spindle forms
•Nucleoli disappear
3. _____________
•Nuclear envelope fragments
•Microtubles attach to
kinetochores on centromere
Fig. 12.6 right
Mitosis
4. __________
•Sister chromatids
arranged in “Plate”
by spindles
5. _______
•Centromeres divide
•Chromosomes pulled
to poles
6. ____________________
•Nuclei begin forming
•Chromatin relaxes
•Cytokinesis begins
4. The _______________ distributes
chromosomes to daughter cells
• The ________________:
• fibers composed of ________________ and associated proteins
• is a major driving force in ____________.
• Assembled during _____________ from cytoskeleton components.
• The spindle fibers elongate by incorporating more subunits of the protein
tubulin.
• Assembly of the spindle microtubules starts
in the ______________.
• As the spindle fibers grow from them, the
centrioles are pushed apart.
• By the end of prometaphase they develop as
the ___________ at opposite ends of the cell.
•_______________ (at centromere) are
attachment points to spindle
Fig. 12.7
5. Cytokinesis divides the cytoplasm
Fig. 12.9a
• ______________
• follows ___________.
• In animals- A contractile
ring of _______
microfilaments and the
motor protein ______ form
to pinch the cell in two.
• In plants- vesicles
from the Golgi coalesce at
the metaphase plate,
forming a ___________.
• The plate enlarges until its
membranes ______.
Fig. 12.9b
6. Prokaryotes reproduce by ___________,
not mitosis.
• Bacterial genes located on a single
chromosome which consists of a
circular DNA molecule and
associated proteins.
• In binary fission, chromosome
replication begins at one point
in the circular chromosome,
the _________________ site.
• These copied regions begin to
move to opposite ends of the
cell.
• Mechanism is unknown
• _____________
are unknown in
bacteria.
Fig. 12.11
7. A molecular control system drives the
cell cycle
• The _______ and _______ of cell division varies with
cell type.
• Skin cells divide often, mature nerve and muscle cells not at all
• The cell cycle is
driven by specific
__________ signals.
• Evidence-Fusion of an
M phase and a G1
phase cell, induces the
___nucleus to start __
phase.
Fig. 12.13
• The distinct events of the cell cycle are directed by
a distinct cell cycle ___________________.
Fig. 12.14
Three major checkpoints are found
in the __, ___, and __ phases.
A ___________ in the cell
cycle is a critical control
point where stop and go
signals regulate the cycle.
If it does not receive a go-ahead
signal, the cell exits the cycle and
switches to a nondividing state, the
__ phase.
•Most human cells are in the G0
phase
What controls cell cycle?
• Answer- ______________ regulate cell cycle by activate
or deactivate other proteins by _________________.
But these kinase levels remain constant throughout cell cycle.
So what activates the kinases?
Kinase
Fig. 12.16a
Answer- ______.
•Level of cyclin proteins
fluctuate cyclically.
• The complex of kinases and
cyclin forms _____________________________
• ______ levels rise sharply
throughout __________, then fall
abruptly during _________.
MPF is a __________ complex
• ____ (“maturation-promoting factor”) triggers the
cell’s passage past the ___ checkpoint to the __
phase.
• MPF…
• _______________ by phosphorylating a variety of
other protein kinases.
• ___________
______________ of
the nuclear envelope.
• ______________
_______________
Fig. 12.16b
Other cyclins and cdks are involved at other cell cycle checkpoints
8. 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 _____.
Fig. 12.17
• 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
container.
• If a gap is created, the
cells will grow to fill
the gap.
Most animal cells also exhibit
____________________ for
cell division.
•Must be anchored to a __________,
typically the ________________ of a tissue
Fig. 12.17
9. Cancer cells have escaped from cell cycle
controls
•Cancer cells are free of both 1- __________________________
and 2- ______________________.
• Cancer cells divide excessively and invade other
tissues because they are free of the body’s control
mechanisms.
• If and when cancer cells stop dividing, they do so at
random points, not at the ________________ in the cell
cycle.
• 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
transformed cells.
• However, cells that evade destruction proliferate to
form a ___________, 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
Fig. 12.19
• Treatments for metastasizing cancers include __________
____________ and _______________ with toxic drugs.
• These treatments target actively ____________ cells.