Transcript Video #: Cancer and its Causes Go to this site: http://www.learner

Video #: Cancer and its Causes
Go to this site: http://www.learner.org/resources/series187.html
Scroll down & Find “ Session 8: Cell Biology & Cancer
Click 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
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(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 Cells
Telomeres, 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
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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
Image of Telomeres-notice light
Blue Regions