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!

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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

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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

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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