Announcements
Text Readings
in Lewis
Chapter 9, The Cell Cycle - Starving a Tumor, pg. 145 -
Cell Cycle Control and Cancer, pg. 153--1561
Chapter 13, DNA Structure and Function - Gene Mutation, pgs. 249-252
The "Reviewing Concepts" boxes are valuable summaries of the main
ideas in these sections of the text.
You have open access (no log-in or password needed) to instructional
materials on the Text web site. Select the text chapter you want and
use the links to the e-learning modules or other available materials.
There is also a collection of study materials called the "Essential
Study Partner" that you may find useful.
Web Crossing
You may also ask questions and see answers to your classmates'
questions in Web Crossing in the "Talk to Carl and Ed" discussion.
Objectives:
The content of today's lecture will help you answer question #1 on
this assignment:
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
-
Transplantability
- Genetic mutability
-
Dedifferentiation
- Loss of contact inhibition
-
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)
Proto-oncogenes are normal genes that we all have. They normally
control cell division or cell death.
- Oncogenes are "cancer genes" that produce unregulated cell growth by
stimulating cell division or preventing cell death. 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?
- Two-Hit Hypothesis Slide from The National Cancer Institute
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