Download The Cell Cycle

The Cell Cycle
Skeleton Notes
Objectives:
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Sequence the events of the Cell Cycle
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Distinguish between Mitosis and Cytokinesis
 Describe and Diagram the events of Mitosis from prophase to telophase
Why Do Cells Divide?
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The process of Cell growth, division and replication is known as the cell
cycle.
Cells division is important for the ____________ and ___________ of
tissue.
In single celled organisms this process is a means of
__________________.
It is also important for the _________________ of cells into tissues.
It is also important for maintaining the size of cells so they do not outgrow their capacity to live and function.
Why are cells small?
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Most cells are small because they work more efficiently at getting
nutrients and processing energy at a small size.
A small cell has a greater amount of _________ ______ with respect to
it’s _____________ of cytoplasm and can therefore absorb nutrients more
efficiently than a large cell.
Nutrients like oxygen, and other materials a cell requires must enter
through it surface. As a cell grows larger at some point its surface area
becomes too small to allow these materials to enter the cell quickly
enough to meet the cell's needs.
The Cell Cycle (overview)
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Traditionally, the cell cycle has been divided into 4 stages:
_____________, ____________, ____________, ____________.
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M= ___________ and is defined as the division of the nucleus
G1 (gap one) and is a period of initial ________________
S (synthesis) is the period when ______ is being replicated.
G2 (gap 2) is a second period of __________ in preparation for division.
G1, S, G2 consume the largest amount of time in the life cycle of a cell.
This period of time between divisions is known as ________________.
The Cell cycle is an endless repetition of mitosis, cytokinesis, growth, and
chromosomal replication.
Interphase
G1 Phase or the Gap 1 Phase
 The newly formed daughter cell increases in _________ and ________.
 _________________ are replicated.
 The cell synthesizes the necessary enzymes and proteins needed for cell
growth.
 DNA consists of a single unreplicated helix uncoiled in the form of
_________________.
 In the G1, the cell may be growing, active, and performing many intense
biochemical activities.
S Phase or he Synthesis Phase
 _________ and chromosomal proteins are replicated.
 This phase lasts a few hours.
G2 phase of the Gap2 Phase
 Occurs between ___________ and ___________.
 The proteins that form the spindle fibers are synthesized which are used
to move the chromosomes in mitosis.
MITOSIS
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Duplication and division of the ___________.
The M stage (Mitosis) has four phases; Prophase, Metaphase, Anaphase,
and Telophase.
Another process divides the cytoplasm and organelles -______________.
Chromosome Structure
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All Eukaryotic cells contain DNA in the form of distinct_______________.
Human somatic (body) cells have ____ chromosomes (23 pairs).
During division, a copy of each of the chromosomes is inherited by each
new cell. Each copy is called a _______________ _________________.
During S (synthesis) each chromatid (single DNA) replicates to form a
Chromosome.
The two DNA molecules (sister chromatids) are held together at a region
known as the __________________.
A segment of DNA is known as a ______________.
A chromosome is made up of many 1000’s of genes.
PROPHASE
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______________ condense; “supercoiling” .
The chromosomes get more compact and become__________.
_________________ _____________ breaks down and disappears.
Each chromosome is made up of two sister chromatids and these two
chromatids are held together by a centromere (kinetochore).
PROMETAPHASE
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Nuclear envelope Fragments.
Microtubules of the spindle can now invade the nucleus and interacts
with the chromosomes.
The two __________________ that were fairly close together move the
opposite poles of the nucleus.
Spindle fibers extend from the poles to the __________________.
METAPHASE.
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The chromosomes line up on the ________________ plane.
This lies in the middle of the spindle apparatus and is perpendicular to its
axis.
ANAPHASE
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Anaphase begins when the spindle apparatus starts pulling the
___________________ to the opposite poles.
The daughter kinetochores move apart dragging the ______________
_________________ (each now a single strand) to the poles.
Two cells begin to form.
TELOPHASE
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Telophase is the reverse of Prophase , but there are now two nuclei
instead of one.
Chromosomes decondense
__________ ______________ reappears.
__________ ___________ becomes disorganized and break down.
The cell pinches in the middle, beginning the formation of the two cells.
CYTOKINESIS; DIVISION OF THE CYTOPLASM
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The last and _____________ stage of the cell cycle
Separation of the ___________ and ____________.
Animal cells
 Cytokinesis usually begins with a __________ ________ at the
metaphase as an indentation in the surface of the cell.
 It looks as though the cell membrane were being pulled toward the
middle, as if a thread were being wrapped around the cell and being
tightened.
Plant cells
 At the time of telophase, small membraneous vesicles forms a double
membrane, which is called the __________ ____________.
 It forms across the midline of the plant cell from the inside out where
the equatorial plane was located.
REGULATION OF THE CELL CYCLE
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Different types of cells take different amounts of time to complete the cell
cycle.
Some cells, like nerve cells, do not go through the cell cycle and no longer
divide.
If cells divide too rapidly, it disrupts the function of the tissue and is
referred to as ________________.
It is important that cells divide only upon reaching a certain size.
Depletion of nutrients, changes in temperature, and pH can stop a cell
from growing and dividing.
The density or the touching other cells (_________ _________) can
control cell division and external regulators of cell growth and division.
The division of cells is ultimately controlled by _______________.
Proteins known as _____________ are produced when certain genes are
“turned on” and regulate the growth and division of cells internally.
Abnormal Cell Division
Cancer cells
 Cancer cells do not respond to normal cell division controls.
 Some cancers are genetic and are caused by ________ that produce too
many ____________ proteins.
 They divide excessively and ignore density-dependent inhibition.
 Cancer cells can go on dividing indefinitely.
 Most mammalian cells will divide about 20-50 times before many stop,
age and die. However, there is a line of laboratory maintained cancer
cells that have been dividing since 1951.
 ________________ _______________ include things like nicotine, Uvb
radiation, PCB’s (polychlorinated benzenes) have an effect on the genes
and ultimately can cause cancer.