Biology 100/101
Lecture 17
Human Genetic Disorders, Cancer, DNA, and Proteins
(Print Version)

Announcements &
Assignments

Lecture Objectives

Web Resources

How Cancer
Grows

The Life
of a Cell

The Control
of Cell Division

Cell Division
in Cancer Cells

Cancer Treatments

Biomarkers

Lecture Syllabus

IB 100/101 Home Page


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 Sarah 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:

  1. Describe the mechanisms by which cell division is controlled in your body.

  2. List the distinguishing characteristics of a cancer cell and describe the ways in which a cell may be triggered to become cancerous.

  3. Describe the changes in genes and gene expression that lead to cancer.

  4. Describe the role of proto-oncogenes, oncogenes, and tumor supressor genes in the development of cancer.

  5. Explain the "two hit" hypothesis for cancer development.

  6. Explain how an understanding of the controls of the cell cycle might facilitate the development of cancer treatments.

Web Resources

How Cancer Grows, from NOVA

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)

Control of Cell Division

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.

  • Cellular Clock - Telomeres (Scientific American)

  • Effect of Neighboring Cells - Contact Inhibition

  • Extra Cellular Influences

    • Hormones

    • Growth Factors

  • Intracellular Influences

    • Kinases and Cyclins

Cell division in cancer cells

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

Cancer Treatments

Biomarkers and Early Detection and treatment of Cancer

  • Often times cancer has already spread (metastasized) before a tumor can be detected by physical exam or by imaging techniques.

  • Scientists are now attempting to find biomarkers that wil help them detect cancer at an early stage.

  • Biomarkers may provide an avenue to disrupt the abnormal gene activity of cancer cells and put the cancer cells back on a track to normal activity.

  • The use of Gene Chips or Micro Arrays to compare gene activation in tumor cells and normal cells.

    • One way to find biomarkers is to find out which genes are active (or inactive) in cancer cells that are not active (or active) in normal cells of the same tissue.

    • Gene Chips from IB 100/101 lecture #19.