Announcements
Text Readings
in Lewis |
Chapter 8 all +
Starving a Tumor, pgs. 137-138
causes, pgs. 152-154
Chapter 13
Gene Mutation, pgs. 255-260
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The "Mastering Concepts" boxes are valuable summaries of the main
ideas in these sections of the text.
Answers to many of these questions can be found at the Text On-Line Learning Center
You may also ask questions and see answers to your classmates'
questions in Web Crossing in the "Talk to Ross and Ed" discussion.
Objectives:
After studying this material you should be able to:
- Describe the mechanisms by which cell division is controlled in your
body.
- List the distinguishing characteristics of a cancer cell and
describe the ways in which a cell may be triggered to become
cancerous.
- Describe the changes in genes and gene expression that lead to
cancer.
- Describe the role of proto-oncogenes, oncogenes, and tumor supressor
genes in the development of cancer.
- Explain the "two hit" hypothesis for cancer development.
- Explain how an understanding of the controls of the cell cycle might
facilitate the development of cancer treatments.
Web Resources
Characteristics of Cancer Cells
- Loss of cell cycle control
- Heritability
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Transplantability
- Genetic mutability
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Dedifferentiation
- Loss of contact inhibition
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Angiogenesis (in growing tumours)
- Ability to spread
(metastasize)
The Life of a Cell:
Cell Division, Cell Maturation, and Cell Death (Apoptosis)
from
CancerQuest.org
Cells normally have built in systems that check to be sure the cell
is OK before initiationg cell division. Proteins check for complete DNA
replication, damaged DNA, and adequate nitrients. If the checks
indicate the cell is not ready to divide it does not.
Cells normally divide when told to do so by some outside influence,
like a hormone or growth factor. Cells also normally respond to signals
that tell them to stop dividing.
Cancer is often the result of some genetic loss of control of the
cell cycle. Genetic changes by mutation or chromosome abnormalities in
a cell result in cells that divide when they should not be dividing.
The Genes of Cancer from CancerQuest.org
- Proto-oncogenes (good) and Oncogenes
(bad)
- Oncogenes are "cancer genes" that produce unregulated cell growth.
They are the result of mutations in normal cell division control genes.
These normal genes are called proto-oncogenes. (If something goes wrong
with them they can become oncogenes.)
- Oncogenes act as "dominant" genes in that it takes only one mutated
copy to produce unregulated cell division.
- Tumor suppressor genes
- Tumor supressor genes produce proteins that inhibit cell division if
conditions are not right. Cells would be kept from dividing if the DNA
were damaged, a needed growth factor or hormone were missing, or if
there were defects in the cell division machinery.
- Tumor supressor genes loose their ability to control cell division
when both copies of the gene are damaged by mutation or
chromosomal abnormalities.
- Two-Hit Hypothesis - If it takes mutations in both
copies of a tumor supressor gene on homologous chromosomes in a cell (to
become homozygous recessive), what happens to your chances of developing
cancer if you are born with one mutated copy?
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