1. cell division functions-___________,_____________ and ___________________ cell division requires...
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1. Cell division functions-___________,_____________ and ___________________• Cell division requires the distribution of
_________ genetic material (DNA) to two __________ cells.
Fig. 12.1c
CHAPTER 8Cell Division and Mitosis
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 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.
• The ___________ of the cell cycle alternates with the much longer ________.
• The M phase includes ____ and __________.
• Interphase accounts for ____ of the cell cycle.
3. The mitotic phase alternates with interphase in the cell cycle: an overview
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
G1
G2
S
M
•Chromosome _________ •Chromosomes coiled•Sister ________joined•Mitotic _______ forms•_________ disappear
•Nuclear envelope _________•Microtubles attach to _________ on centromere
Fig. 12.5 left
1. __________ 2. _________3. _____________
Mitosis- 6 phases
•Sister chromatids arranged in “_____” by spindles
4. __________ 5. ________ 6. ________and ____________
•Centromeres divide•Chromosomes pulled to poles
•Nuclei begin forming•Chromatin relaxes•____________ begins
Mitosis
• 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.
4. The ____________ distributes chromosomes to daughter cells
Cytokinesis divides the cytoplasm• ____________
• 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 ______
vesicles converging
5. Prokaryotes reproduce by __________, not mitosis.
• Bacterial genes located on a single chromosome
• 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.
• 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.
6. A molecular control system drives the cell cycle
Fig. 12.12
• The _______ and _____ of cell division varies with cell type.• Skin cells divide often, mature nerve and muscle cells not at all
• The distinct events of the cell cycle are directed by a distinct cell cycle ___________________.
Fig. 12.13
Three major checkpoints are found in the __-___ , and __ phases.
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 G0 phase
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.
Fig. 12.15
• 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
• 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.
8. Cancer cells have escaped from cell cycle controls
•Cancer cells are free of both 1-____________________ and 2-_________________________.
• 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 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.
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