Video #: Cancer and its CausesGo to this site: http://www.learner.org/resources/series187.html

Scroll down & Find “ Session 8: Cell Biology & CancerClick on “VoD” and watch

Reference Pages: Ch. 3 Pgs. 93-96 (old text or 105-107new text

**While watching the video be sure to have a minimum of 15 key statements. Some of your statements should address:

1. What was thought to be the cause of cancer in the earlier years? What do we know today in regards to the causes of cancer?

2. Differences between an Oncogene and a Tumor suppressor gene and what these genes specifically do.

3. The RAS gene and p53 gene and what they do. Which one is a proto-oncogene

4. Why is the p53 gene considered to be the “Guardian Angel of the cell” Give three things that is does.

5. How has the study of Telomeres and the enzyme Telomerase contributed to our knowledge of cancer.

Genes that Cause Cancer(useful when watching the video

• Genes: are the A, T, C, G sequences that are used to make proteins in all of our cells. When genes get “expressed” a portion of the DNA is used to make a particular protein. (**genetic expression = protein synthesis)

• Oncogenes: cause cell division to continue at a faster & faster rate. Other genes are activated that normally are “off”(Ex. From video: ras gene) – seen in 30% of all cancers

• Proto-Oncogenes: normal genes that code for normal cell growth and division

• Tumor Suppressor Genes: normally inhibits cell division and prevents uncontrollable cell growth. Typically, these genes stops tumors from growing. When mutated, this ability is lost.

(Ex. From video: p53 gene) – seen in 50% of all cancers

*Environmental factors can change how genes get expressed

Characteristcs of Cancer(Pg. 95)

• Mitosis gone Haywire (uncontrolled cell division)• Cells develop & no longer have their specialized

function (unable to produce what they are supposed to produce)

• All they do is make more cancer cells• Will induce blood vessels to grow (angiogenesis)• Has the ability to spread (metastasize)• Cells will divide and grow into tumors

– Benign (non-cancerous) vs. -Malignant (cancerous)

Cyclin & MPF Concentrations

Mitotic Clock Mechanisms in CellsTelomeres, Proteins, Cell size (SA), hormones, &

Growth factors

• Telomeres: Segments of DNA (200 repeated sequences of nucleotides) are lost at the tips of the chromosomes with each mitotic event.– (Mitotic clock) the tips of chromosomes wear

down and lose DNA sequences over time.– Six Nucleotide sequence repeated hundreds of

times– 1,200 nucleotides are removed after each mitotic

event

Telomeres• Short, non-coding pieces of DNA• Contains repeated sequences (ie. TTGGGG 20 times)• Can lengthen with an enzyme called Telomerase• Lengthening telomeres will allow more replications to occur.• Telomerase is found in cells that have an unlimited number of cell

cycles (commonly observed in cancer cells)• Artificially giving cells telemerase can induce cells to become

cancerous• Shortening of these telomeres may contribute to cell aging and

Apotosis (programmed cell death)

Ex. A 70 yr old person’s cells divide approx. 20-30X vs an infant which will divide 80-90X

Telomeres