THE CELL CYCLE AND MITOSIS 2Lesson 6January 26th, 2011

REVIEW OF MITOSIS Interphase Prophase Metaphase Anaphase Telophase Cytokniesis

CELL GROWTH AND REPAIRMulticellular organisms are made

up of many different cells. The different types of cells undergo

growth and cell division at different rates.

CELL GROWTH AND REPAIR Nerve cells do not divide once they are

mature Intestine cells divide every 3 days. Cells that are likely to be damaged will be

replaced more often In plants, growth occurs rapidly in the

meristem region. Cells in this region divide every 12 to 36 hours.

FACTORS THAT AFFECT MITOSISLiving organisms respond to

changes in the environment Altitude causes more divisions of

blood cellsPlants bend toward light because the

cells on the opposite side of the light divide faster.

Antibiotics called bacteriostatic drugs can temporarily stop the replication of DNA.

HOW LONG DO CELLS LIVE?The cell cycle regulates how long

a cell lives. Cells die to injury or unrepairable damage. Necrosis

HOW LONG DO CELLS LIVE? A cell that dies as a normal part of a

healthy multicellular organism is regulated and controlled. This is called apoptosis. Example: cells produced to fight

infections die when they are no longer needed.

CANCER CELLS A cell that divides uncontrollably is called a

cancer cell. Cancer cells develop when a change occurs in the cell that affects how that cell divides. When a cell’s DNA is changed, it is known as a mutation.

A cancer cell divides differently from a normal cell.

CANCER CELLS Cancer cells ignore the usual density-

dependent inhibition of growth, multiplying after contact with other cells is made, piling up until all nutrients are exhausted. The cancer cells proliferate to form mass of cancer cells called a tumour. As the tumour grows larger, it begins to release proteins from the cell to attract new blood vessel growth (this is called angiogenesis).

CANCER CELLS VIDEO CLIP

MALIGNANT CANCER CELL VIDEO CLIPHTTP://WWW.YOUTUBE.COM/WATCH?V=5PP4BMM9YNQ

TYPES OF TUMOURS Benign: tumour cells remain at their

original site.

TYPES OF TUMOURS Malignant: some tumour cells send out

signals that tell the body to produce a new blood vessel at the tumour site. These cells not only have a food and oxygen supply, they also have an avenue for escape to a new part of the body - through the new blood vessel and into bloodstream. Cells that break away from the tumour begin to spread to surrounding tissues (via the bloodstream or lymph) and start new tumours = metastasis.

TYPES OF TUMOURS

UNUSUAL FEATURES OF CANCER CELLS Cancer cells are frequently "immortal":

whereas normal cells divide about 50 times and they die, cancer cells can go on dividing indefinitely if supplied with nutrients.

Cancer cells often have unusual numbers of chromosomes or mutations in chromosomes.

UNUSUAL FEATURES OF CANCER CELLS Cancer cells may also have an abnormal cell

surface; instead of "sticking" to its neighbouring cells, cancer calls tend to "round up" and break attachments its neighbours cells, allowing for metastasis.

A=asymmetry B=borders are irregular C=color D=diameter

CARCINOGENS Any substance or energy that causes a

mutation in DNA is called a Carcinogen. There are three types of known carcinogens

1.Viruses – Ex leukemia – cancer of the white blood cells.

2.Radiation – UV rays, nuclear radiation. 3.Hazardous chemicals – toxic chemicals,

chemicals found in cigarettes. With aging free radical are produced in larger

quantities which can damage DNA and cause mutations as well. Aging is not a carcinogen.

COMPARING NORMAL CELLS TO CANCER CELLS

Normal Cells

- Make exact copies of themselves through mitosis

- Reproduce for about 50-60 divisions- Stick Together to form masses of cells as

appropriate- Self destruct when too old or too damaged

COMPARING NORMAL CELLS TO CANCER CELLS

Cancer Cells

- Make exact copies of themselves through mitosis- Do not stop reproducing “Immortal”- Do Not stick together - Behave independently- May move to another location of the body. - Often have unusual numbers of chromosomes or

mutations.

COMPARING NORMAL CELLS TO CANCER CELLS

COMPARING CANCER CELLS AND NORMAL CELLS – DRY LAB Complete and hand in This should be relatively quick which should

allow you time to work on your other work you have not yet handed in.