cell division – mitosis. as the cell grows, its volume increases much more rapidly than the...
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Cell Division –Mitosis
As the cell grows, its volume increases much more rapidly than the surface area.
The cell might have difficulty supplying nutrients and expelling enough waste products.
Cellular Growth
Transport of Substances
Substances move by diffusion or by motor proteins.
Diffusion over large distances is slow and inefficient.
Small cells maintain more efficient transport systems.
Cellular Communications
The need for signaling proteins to move throughout the cell also limits cell size.
Cell size affects the ability of the cell to communicate instructions for cellular functions.
The Cell Cycle
Cell division prevents the cell from becoming too large.
It also is the way the cell reproduces so that you grow and heal certain injuries.
Cells reproduce by a cycle of growing and dividing called the cell cycle.
• http://www.cellsalive.com/mitosis.htm
Interphase is the stage during which the cell grows, carries out cellular functions, and replicates.
Mitosis is the stage of the cell cycle during which the cell’s nucleus and nuclear material divide.
Cytokinesis is the method by which a cell’s cytoplasm divides, creating a new cell.
The Stages of Interphase
The first stage of interphase, G1
The cell is growing, carrying out normal cell functions, and preparing to replicate DNA.
The Second Stage of Interphase, S
The cell copies its DNA in preparation for cell division.
The Third Stage of Interphase, G2
The cell prepares for the division of its nucleus.
The Stages of Mitosis
Prophase
The cell’s chromatin tightens.
Sister chromatids are attached at the centromere.
Spindle fibers form in the cytoplasm.
The nuclear envelope seems to disappear.
Spindle fibers attach to the sister chromatids.
MetaphaseSister chromatids are pulled along
the spindle apparatus toward the center of the cell.
They line up in the middle of the cell.
Anaphase
The microtubules of the spindle apparatus begin to shorten.
The sister chromatids separate.
The chromosomes move toward the poles of the cell.
Telophase
The chromosomes arrive at the poles and begin to relax.
Two new nuclear membranes begin to form and the nucleoli reappear.
The spindle apparatus disassembles.
Cytokinesis
In animal cells, microfilaments constrict, or pinch, the cytoplasm.
In plant cells, a new structure, called a cell plate, forms.
Normal Cell Cycle
Different cyclin/CDK combinations signal other activities, including DNA replication, protein synthesis, and nuclear division throughout the cell cycle.
([http://en.wikipedia.org/wiki/Image:mitosis-flourescent.jpg source and rights])
Quality Control Checkpoints
The cell cycle has built-in checkpoints that monitor the cycle and can stop it if something goes wrong.
Spindle checkpoints also have been identified in mitosis.
• The disease is Progeria, or Hutchinson-Gilford Progeria Syndrome (HGPS), a rare, accelerated aging disease that afflicts children.
Errors in Mitosis
• Errors in mitosis are rare, the process may go wrong, especially during early cellular divisions in the zygote (single, diploid cell resulting form fertilization of egg and sperm).– Mutation. – In nondisjunction, a chromosome may fail to
separate during anaphase.– Occasionally, chromosomes may become
damaged. An arm of the chromosome may be
broken and the fragment lost, causing deletion..
– The fragment may incorrectly reattach to another, non-homologous chromosome, causing translocation.
– It may reattach back to the original chromosome, but in reverse orientation, causing chromosomal inversion.
– It may be treated erroneously as a separate chromosome, causing chromosomal duplication.
– The effects of these genetic abnormalities depend on the specific nature of the error and can range from no noticeable effect at all to organism death.
• Cancer is essentially a disease related to mitosis, involving a breakdown in the regulation process such that there is uncontrolled cell replication
1. A2. B3. C4. D
Which occurs in plant cells but not animal cells during the cell cycle?
A. formation of a cell plate
B. formation of microtubules
C. formation of a cleavage furrow at the equator of the cell
D. movement of chromosomes to the poles of the cell
1. A2. B3. C4. D
This cell has completed what stage of mitosis?
A. anaphase
B. interphase
C. metaphase
D. telophase
1. A2. B3. C4. D
Which diagram shows anaphase?
A. B.
C. D.
1. A2. B3. C4. D
A. interphase
B. prophase
C. metaphase
D. telophase
Which is the first phase of mitosis?
1. A2. B3. C4. D
A. interphase
B. metaphase
C. anaphase
D. telophase
During what phase do the sister chromatids line up in the middle of the cell?
1. A2. B3. C4. D
A. cytokinesis
B. interphase
C. apoptosis
D. mitosis
Which is not a phase of the cell cycle?
1. A2. B3. C4. D
Which can more efficiently supply nutrients and expel waste products?
A. larger cells
B. smaller cells
C. cells with lower surface
area to volume ratio
D. cells shaped like a cube
1. A2. B3. C4. D
At what stage does a cell spend most of its life?
A. cytokinesis
B. interphase
C. mitosis
D. synthesis
1. A2. B3. C4. D
What happens in the cell during cytokinesis?
A. The cell grows and carries out normal functions.
B. The cell copies its DNA and forms chromosomes.
C. The cell’s nucleus and nuclear material divide.
D. The cell’s cytoplasm divides.
1. A2. B3. C4. D
In what stage of the cell cycle does the cell’s replicated genetic material separate?
A. cytokinesis
B. interphase
C. mitosis
D. prophase