Download # Unit 4 LT1

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Unit 4
LT1
Use the diagram to help you to explain why surface area-to-volume (s.a./vol) ratios are important to a dividing
cell.
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When cells divide, their surface area (supply of nutrients
across the plasma membrane) decreases slower, by length2
while volume (metabolic demand) decreases faster by
length3.

Mitotic cell division gives the cell a much more favorable
surface area to volume ratio.
Mrs. Loyd 
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Unit 4
LT1
Create a model to illustrate how prokaryotic DNA is divided for cell reproduction.
What is this process called?
How are the two cells related to each other genetically?
The model presented in class used two large rubber bands twisted together to represent the
circular DNA of a prokaryotic cell.

They adhere to the plasma membrane at the equator of the plasma membrane.

As cytokinesis occurs, the two rings of DNA are pulled apart into their half of the cell.

Two cells are formed this way. It is called binary fission. (“2” – “separating”)

They are genetically identical (except for the plasmid DNA that was divided by chance).
Mrs. Loyd 
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Unit 4
LT2a
Identify the phases of the cell cycle.
 the long, round arrow
 the short, split arrow
 each of the five pie wedges
 the name for the resulting cells
Please do not mark on this paper.
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daughter cells
Mrs. Loyd 
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Unit 4
LT2c
Put the following descriptions of each the events of each of the phases in the proper chronological order.
Cytoplasm is divided by the
“purse-string mechanism”
in animal cells and by creating
a cell plate in plant cells.
1. Chromosomes are single-stranded.
Mitochondria divide
Cell grows: adds membrane for larger membrane-bound organelles.
Supply of monomers and ATP increase.
Includes a checkpoint for readiness.
2. DNA is replicated
Protein production and metabolism on “hold.”
3. Chromosomes are double-stranded.
Mitochondria divide
Cell grows: adds membrane for larger membrane-bound organelles.
Supply of monomers and ATP increase.
Includes a checkpoint for readiness.
4. Nuclear information is arranged and divided
5. Cytoplasm is divided by the “purse-string mechanism” in animals and by creating a cell plate in plant cells.
Mrs. Loyd 
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Unit 4
LT2d
Cancer is considered
a disease of the cell
cycle.
Explain why.
Cancer cells divide out of control. They
are not governed by the chemical
messages that control the cell cycle.
Sometimes, mutations cause the loss of
expression of the p53 or guardian angel
gene/protein which protects the individual
by destroying cancerous cells.
If this is then followed by a mutation for
over-expression of the “divide” command
(the Ras gene/protein), the cell becomes
cancerous and divides until a tumor forms.
Mrs. Loyd 
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Unit 4
LT3
Use your knowledge of mitotic events to identify and label each phase of mitosis.
This cell is in the cell cycle phase called interphase; it is not in mitosis.
Prophase: Chromosomes are distinct but nuclear envelope and nucleolus are still visible.
of
Metaphase: Chromosomes form a single file line at the metaphase plate through the equator
the cell. “Chromosomes met at metaphase”
Anaphase: Chromosomes have moved to opposite poles but no cell plate is yet visible. Notice
the spindle fibers.
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Name the parts of the chromosome. Use this word bank:
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