why do cells divide?. quiz 1.where does dna synthesis occur ?(what organelle?) 2.what does helicase...
TRANSCRIPT
Why do cells divide?
QUIZ
1. Where does DNA synthesis occur ?(what organelle?)
2. What does Helicase do? DNA polymerase do?
3. What is the purpose of DNA synthesis?
4. Write down this DNA’s complimentary strand1. G A T A C A
Since we say family members are “blood” relatives, does that mean we share the same blood?
• You share no blood with anyone....not even your mother and father! Your family shares DNA.
• 1⁄2 of your DNA came from your mother (egg) and 1⁄2 from your father (sperm).
• The process that made this possible is MEIOSIS which makes the sperm and egg.
• A fertilized egg then grows into an organism by a different process of cell division called MITOSIS.
Cells divide to maintain a workable volume to surface area ratio
Cells divide to maintain a workable volume to surface area ratio
Volume is the amount of space inside of a cell.
This would include the cytoplasm and all of the organelles.
Cells divide to maintain a workable volume to surface area ratio
Surface area is the total amount of exterior which is exposed to the environment around the cell.
This would include the outside of the cell membrane.
Cells divide to maintain a workable volume to surface area ratio
Volume increases faster than surface area.
Cells divide to maintain a workable volume to surface area ratio
The surface area must be large enough for a sufficient amount materials to enter the cell.
The materials must enter quickly enough that all of the cell will get what it needs.
Thus, a larger surface area: volume ratio is preferred.
Cells stay small to keep the rate of diffusion fast!
Fill It In …
EXPLAIN which of the cell sizes pictured is preferable.
Cells divide to make more cells
Growth of a multicellular organism requires the addition of cells
Larger organisms do not necessarily have bigger cells, but they will have more cells than smaller organisms.
Cells divide to make more cells
Repair of damaged tissues by replacement of cells lost due to injury or cell death requires cell division.
A healthy cell will divide to replace the lost cell(s).
Mitosis
Fill It In …
2 reasons that cells need to divide:
1.
2.
Cells divide to make more cells
Cell division occurs at different rates depending on the organism and the type of cell.Plant root cells would
divide more rapidly because this is an area of active growth
Cell division occurs at different rates
Some nerve cells enter a phase of no divisionCalled G0
Why brain and nerve damage is often nonreversible
Cell division occurs at different rates
Some bacteria cells divide very rapidly
For example, E. coli can divide every 20 minutes in ideal conditions.
How do cells divide?
Prokaryotic vs Eukaryotic Division
How do cells divide?The result of all cell
division is the production of daughter cells.
In order for daughter cells to contain enough DNA, the genetic material (DNA) of the parent cell must be copied.
How do cells divide?
Prokaryotic division differs from eukaryotic division because prokaryotic cells do not contain a nucleus or membrane-bound organelles.
How do cells divide?
Eukaryotic division requires the replication of the nucleus and genetic material (DNA) as well as the allocation of the organelles into each daughter cell.
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Reason that prokaryotic cell division is simpler than eukaryotic cell division …
Eukaryotic Cell Cycle & Mitosis
Interphase is the “normal” part of the cell cycle.
The cells spend most of the cycle (life of the cell) in interphase.
There are three stages in interphase
G1 - Cell increases in size and synthesize new proteins and organelles
There are three stages in interphaseS - DNA is replicated
During most of interphase, DNA exists in a “relaxed”, stringy form called chromatin
After being copied, there are two complete copies of the DNA in the cell.
These copies are attached to each other.
There are three stages in interphaseS - DNA is replicated
Each copy of DNA is called a chromatid.
The two chromatids are attached in a region celled the centromere.
At this point in interphase, the chromatids are coiled/condensed
The entire structure is called a doubled chromosome.
Structure of Chromosomes
There are three stages in interphase
G2 - organelles and molecules required for cell division are produced
Fill It In …
Differentiate between …
Chromatin -
Chromatid -
Chromosome -
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On the diagram of the cell cycle, HIGHLIGHT the stages that are part of Interphase.
DRAW the Cell Cycle
Stages of Mitosis (Eukaryotic Cell Division)
ProphaseCoiled chromosomes
become visibleNuclear membrane is
broken downSpindles (protein fibers that
attach to chromosomes and aid in chromosome movement) start to form
Stages of Mitosis (Eukaryotic Cell Division)Metaphase
Spindle fibers attach to the centromere regions
Chromosomes are moved to the Middle of the cell
Stages of Mitosis (Eukaryotic Cell Division)Anaphase
Spindle fibers shortenDoubled chromosomes
are separated into chromatids
Chromatids begin to move to opposite poles/ends of the cell
Stages of Mitosis (Eukaryotic Cell Division)
TelophaseSpindle fibers are broken
downNuclear membrane
begins to form around the clusters of chromatids at each pole of the cell.
Cytokinesis
Cytokinesis is the separation of the cytoplasm (including all organelles) into two identical daughter cells.
Cytokinesis
Animal cells constrict in the middle to pinch apart forming two different cells.
Cytokinesis
Plant cells also produce a cell plate dividing the two cells.
This cell plate will become the cell wall
MITOSIS Animation
Fill It In …
Summary of the cell cycle1. Interphase
1. .2. .3. .
2. Mitosis1. .2. .3. .4. .
3. .
Mitosis & Cancer
Typically, cell division is controlled by genes in the cell, contact with other cells, and available nutrients in the environment.
(molecules are found on the surface of the cell)
Mitosis & Cancer
Cancer is a class of diseases characterized by uncontrolled cell division and the ability of these cells to invade other tissues (metastasis).
Mitosis & CancerCancer occurs when the
genes that control cell division do not function properly.
This may occur because of an inherited genetic defect, a spontaneous genetic mutation, or mutation caused by environmental factors.
Cancer and the Cell Cycle
Cancer
Cancer Institute
The Cell Cycle and Cancer
The Stages of the Cell Cycle
Cancer- Cancer cells do not respond to the signals that
regulate cell division Creates a tumor (or mass of cells) that can
migrate throughout the bodyCyclin- regulates the cell cycle
There are several factors that regulate the cell cycle and assure a cell divides correctly.
1.Before a cell divides, the DNA is checked to make sure it has replicated correctly. (If DNA does not copy itself correctly, a gene mutation occurs.
2. Chemical Signals tell a cell when to start and stop dividing.
Neighboring cells communicate with dividing cells to regulate their growth also.
Cancer is a disease of the cell cycle. Some of the body’s cells divide uncontrollably and tumors form.
Tumors in Liver
Tumor in Colon
DNA mutations disrupt the cell cycle.
Mutations may be caused by:
1. radiation 2. smoking 3. pollutants 4. chemicals 5. viruses
While normal cells will stop dividing if there is a mutation in the DNA, cancer cells will continue to divide with mutation.
Fourth orlater mutation
Third mutation
Second mutation
First mutation
Uncontrolled growth
Cell Suicide or Apoptosis
Cell damage—no repair
Due to DNA mutations, cancer cells ignore the chemical signals that start and stop the cell cycle.
Due to DNA mutations, cancer cells cannot communicate with neighboring cells. Cells continue to grow and form tumors.
Skin cancer
ABCD of Cancer
Regions of Highest IncidenceU.K.:Lungcancer
Regions of Highest Incidence
UK:Lungcancer
JAPAN:Stomachcancer
CHINA:Liver cancer
AUSTRALIA:Skin cancer
US:Colon cancer
CANADA:Leukemia
BRAZIL:Cervicalcancer
Cancer by State
Mitosis and Cancer1. Typically, cell division is controlled by genes in the cell,
contact with other cells, and available nutrients in the environment.
2. Cancer is a class of diseases characterized by uncontrolled cell division and the ability of these cells to invade other tissues.
How Cancer Develops
Treating Cancers
Cancer treatments include surgery, chemotherapy, radiation, or lasers.
SUMMARY
Normal Cell Division
1. DNA is replicated properly.
2. Chemical signals start and stop the cell cycle.
3. Cells communicate with each other so they don’t become overcrowded.
Cancer Cells
1. Mutations occur in the DNA when it is replicated.
2. Chemical signals that start and stop the cell cycle are ignored.
3. Cells do not communicate with each other and tumors form.
Vocabularycancer: term used to indicate a disease
characterized by abnormal cell growthmutagen: environmental factor that causes
mutationscarcinogen: cancer-causing agenttumor: mass of growing tissue
benign: does NOT invade surrounding cellsmalignant: spreads into nearby tissues
metastasis: spread of malignant cellsoncogene: gene that causes cancerous growth
Fill It In …
Cancer is caused by uncontrolled _______ ___________, which may occur because of
1.
2.
3.
Check Yourself!
1. Why is a large surface area: volume ratio preferable?
2. Name three reasons cells must divide.
3. Why is eukaryotic cell division more complex than prokaryotic cell division?
4. What are the two basic stages of the cell cycle?
5. How is the genetic material “prepared” for cell division during interphase?
6. How many daughter cells are produced as a result of mitosis, and how do these cells compare to the parent cell?
7. How are mitosis and cancer connected?
Check Yourself!
1. Why is a large surface area: volume ratio preferable? KEEPS THE RATE OF CELL DIFFUSION FAST
Check Yourself!
2. Name three reasons cells must divide.
GROWTH
REPAIR
(ASEXUAL REPRODUCTION)
Check Yourself!
3. Why is eukaryotic cell division more complex than prokaryotic cell division?
EUKARYOTIC CELLS CONTAIN A NUCLEUS AND MEMBRANE-BOUND ORGANELLES
Check Yourself!
4. What are the two basic stages of the cell cycle?
INTERPHASE & MITOSIS
Check Yourself!
5. How is the genetic material “prepared” for cell division during interphase?
CHROMATIN CONDENSES AND FORMS TWO CHROMATIDS CONNECTED BY A CENTROMERE
THIS FORMS A DOUBLED CHROMOSOME
Check Yourself!
6. How many daughter cells are produced as a result of mitosis, and how do these cells compare to the parent cell?
2 CELLS ARE PRODUCED
THEY ARE GENETICALLY IDENTICAL TO THE PARENT CELL
Check Yourself!
7. How are mitosis and cancer connected? CANCER IS CHARACTERIZED BY UNCONTROLLED CELL DIVISION