Chp. 11 - Cell Cycle
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uncontrolled cell growth leads to?
2 types of cell division
mitosis and meiosis
What does meiosis do?
Produces haploid daughter cells
Basis of sexual reproduction
What does mitosis do?
Produces daughter cells that are identical to parent cells
Produces Somatic cells (Body Cells)
What is cytokinesis?
the division of the cytoplasm into two daughter cells
What is mitosis reponsible for?
Chromosomes contain what?
DNA contains what?
Growing cells cycle between which two phases?
Mitotic phase and Interphase
Mitotic phase is the
Interphase is the
2 key events of cell cycle
-replication - chromosomes are copied
-splitting copied chromosomes into daughter cells
In what stage does DNA replication occur
What is the S phase?
The stage where DNA replication occurs
Interpahse has how many gap phases
2 phases where no DNA synthesis occurs
What happens during gap phase?
Organelles replicate and additional cytoplasm is made
What are the 4 phases of the cell cycle?
what is a chromatid?
each of two replicated strands
What happens before mitosis?
What happens in interphase?
Chromosomes replicate and are now composed of 2 sister chromatids
what happens in prophase?
mitotic spindles begin to form from microtubule organizing center
what happens in prometaphase?
nuclear envelope breaks down
spindle fibers attach to chromosomes at kinteochore
what happens in metaphase?
chromosomes are lined up in the middle of the cell
What happens in anaphase?
Sister Chromatids seperate and are pulled to opposite poles
What happens in telophase?
nuclear envelope reforms
spindle apparatus is disintegrates
chromosomes begin to decondense
What happens during cytokinesis in animals?
Actin-Myosin ring causes plasma membrane to pinch in a cleavage furrow forming 2 daughter cells
what happens during cytokinesis in plants?
vesicles are transported from golgi apparatus to middle of dividing cell to form cell plate.
How do chromosomes move during mitosis?
deattach-move-attach cycle of motor proteins allow chromosomes to walk
Why can't chromosomes walk on their own?
Tubulin subunits within the kinetochore are lost therefore shorteining microtubules
what is the Go phase
when non-dividing cells get stuck in G1 phase.
G1 pahse can be eliminated in what type of cells?
rapidly dividing cells
What induces mitosis?
Mitosis promoting factor (MPF)
Where is MPF found
Cytoplasm of M phase cells
what are the 2 subunits of MPF
Cyclin and protein kinases
what is Cyclin?
what do protein kinases do?
catalyze the transfer of phosphate from ATP to protein
What can activated MPF do?
phosphorylate chromosomal proteins, start M phase
phosphorylate nuclear lamins, start nuclear envelope breakdown
phosphorylate microtubule associated proteins, activate mitotic spindle
phosphorylate enzymes that degrades cyclin, cyclin concentration declines
What is a cell-cycle checkpoint?
Point in cell-cycle where regulatory molecules determine if a cell proceeds with cell division
What are the 3 checkpoints?
What is the purpose of the G1 checkpoint?
Determines whether cells continue to divide or enter G0 phase
4 factors that determine whether cell passes G1 checkpoint
-cell size - cell must be large enough to split
-nutrient condition - cell must have enough food to grow
-cell must be able to receive social signals from other cells
-action of tumor suppressors - regulatory proteins that can stop cell cycle
What is the first and most important checkpoint?
What is the purpose of the G2 checkpoint
to stop cells from growing if their DNA is damaged or chromosome replication is not working properly
what is the purpose of the M phase checkpoint?
To stop cell growth if chromosomes are not properly attached to mitotic spindle
What does the M phase checkpoint prevent?
incorrect chromosome seperation that could give daughter cells the wrong number of chromosomes
What is the purpose of cell checkpoints?
To prevent the division of cells that are damaged or have other problems.
What is cancer?
uncontrollable cell growth that invades nearby cell tissues and spreads to other sites in the body
What are the two defects found in cancerous cells?
-proteins required for cell growth are always active
-tumore supressor genes are prevented from shutting down the cell cycle
how does a tumor form?
when one or more cells in an organism divide uncontrollably
what are benign tumors?
noninvasive and noncancerous tumors
what are malignant tumors?
invasive tumors that can spread throughout the body and initiate secondary tumors
what is metastasis?
when cancer cells detach from the original tumor and invade other tissues
Cancer cells are thought to come from cells with defects in what checkpoint?
How does social control play a role in cell division?
cells respond to signals of other cells so they only divide when their growth benefits the whole organism
What are growth factors?
Polypeptides or small portiens that signal other cells to grow
How are cancer cells no longer subject to social control at the G1 checkpoint?
Cancer cells divide without Growth Factors
How do growth factors initiate cell division?
they trigger cyclin synthesis which activates cyclin-Cdk complexes, leading to activation of S-phase proteins
Most cancers arise from defects in what?
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