T HE C ELL C YCLE AND M ITOSIS 2 Lesson 6 January 26 th, 2011

R EVIEW OF MITOSIS Interphase Prophase Metaphase Anaphase Telophase Cytokniesis

C ELL G ROWTH AND R EPAIR Multicellular organisms are made up of many different cells. The different types of cells undergo growth and cell division at different rates.

C ELL G ROWTH AND R EPAIR 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.

F ACTORS THAT A FFECT M ITOSIS Living organisms respond to changes in the environment Altitude causes more divisions of blood cells Plants 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.

H OW LONG DO C ELLS L IVE ? The cell cycle regulates how long a cell lives. Cells die to injury or unrepairable damage. Necrosis

H OW LONG DO C ELLS L IVE ? 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.

C ANCER C ELLS 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.

C ANCER C ELLS 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 ).

C ANCER C ELLS V IDEO C LIP

M ALIGNANT C ANCER CELL V IDEO CLIP HTTP :// WWW. YOUTUBE. COM / WATCH ? V =5 P P4 B M M 9 Y NQ HTTP :// WWW. YOUTUBE. COM / WATCH ? V =5 P P4 B M 9 Y NQ

T YPES OF T UMOURS Benign : tumour cells remain at their original site.

T YPES OF T UMOURS 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.

T YPES OF T UMOURS

U NUSUAL FEATURES OF C ANCER C ELLS 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.

U NUSUAL FEATURES OF C ANCER C ELLS 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

C ARCINOGENS 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.

C OMPARING N ORMAL C ELLS TO C ANCER C ELLS Normal Cells -Make exact copies of themselves through mitosis -Reproduce for about divisions -Stick Together to form masses of cells as appropriate -Self destruct when too old or too damaged

C OMPARING N ORMAL C ELLS TO C ANCER C ELLS 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.

C OMPARING N ORMAL C ELLS TO C ANCER C ELLS

C OMPARING C ANCER C ELLS AND N ORMAL C ELLS – D RY L AB 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.