Oncogenes and TumorSuppressor Genes

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Oncogenes and Tumor-Suppressor Genes

• Group 5Blakeley Thomas
• Holly Doebbler

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What is Cancer?

• A disease of the cell cycle.
• A mutation in cellular DNA, causing unregulated
  cell growth which is -increase in cell
  division -change in cell location -decrease in
  cell mortality -cell differentiation
• Common types lung, prostate, breast, skin,
  ovarian, leukemia, and non-Hodgkin's lymphoma.

Lung cancer http//www.mesothelioma-lung-cancer.or
g/lung-cancer-photo.html
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What Factors Cause Unregulated Cell Growth?

• Mutagens and Carcinogens are the most common
  factors that cause genetic mutations and changes
  in protein concentration
• Mutagens agents that cause a genetic mutation
• Carcinogens agents that promote cancer

http//en.wikipedia.org/wiki/DNA
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What Increases Cancer Development?

• Genetic predispositions oncogenes and
  tumor-suppressor genes
• Germ line mutations
• Environmental Factors tobacco smoke, radiation,
  certain viruses, alcohol, and estrogen
• Spontaneous mutations during transcription and
  translation

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What is an Oncogene?

• First discovered in the avian RNA virus RSV, Rous
  sarcoma virus.
• Carried a src gene. c-src is the healthy version
  (known as a proto-oncogene), v-src is the viral
  (damaged) version
• Oncogene is a gene that induces malignant cell
  growth by changing the behavior of a cell
• It is dominant requires only one mutated gene
  for the oncogene to become active (increase the
  probability of cellular mutation)

http//en.wikipedia.org/wiki/ImageRespiratory_syn
cytial_virus_01.jpg
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Proto-Oncogenes

• Genes that trigger normal cell growth and control
  cell division.
• can become oncogenes when they begin causing
  unnecessary active mitosis
• Possible Activation Methods
• mutation that changes the protein structure
• increase in protein concentration
• Mutations include point mutations,
  amplification, and rearrangement of bases

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How Does Increased Protein Concentration Occur?

• A proto-oncogene fuses with another gene
  (translocation mutation) and they are transcribed
  and translated together, increasing cell
  division.
• Proto-oncogenes send signals to neighboring cells
  telling them to divide and proliferate

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What are Tumor-Suppressor Genes?

• Genes that send signals to cells that decrease
  the probability of tumor formation
• Promotes apoptosis (programmed cell death) and
  regulation of the cell cycle
• Recessive two mutated T-S genes are required
  before an effect (not suppressing tumor cells) is
  noticed

http//www.scq.ubc.ca/?p350
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How do T-S Genes Work?

• Do not allow a cell to divide if DNA is damaged
  require the DNA to be repaired first
• If DNA cannot be repaired, the T-S gene initiates
  apoptosis.
• Interrupts cellular differentiation (process of a
  stem cell becoming a specialized cell type)
• This decreases unhealthy and mutated DNA from
  replicating and spreading, inhibits metastasis
  (tumor cell spreading from one location to
  another), and stops unregulated cell growth.

This fly has a defective Mats gene, which has
resulted in poorly controlled tissue growth.
Instead of the normal flat shape on the top of
its head between the left eye (shown) and the
right eye, this fly has a large lump of tumor
tissue. PHOTO CREDITS Laboratory of Zhi Chun Lai
at Penn State
http//www.eurekalert.org/pub_releases/2005-03/ps-
ntg030905.php
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T-S Genes and Cancer Formation

• If the section of DNA that codes for the T-S gene
  gets deleted or mutated, the chances of that cell
  turning into a tumor cell increases
• T-S Genes do not affect the expression of
  oncogenes
• However, the expression of the oncogene alone is
  not enough to give a cell tumor-forming potential

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T-S Gene p53

• Activated by a series of stressors (hypoxia and
  UV radiation)
• Mutation of the p53 gene is in 50 of cancers
• Functions
• Division regulation and apoptosis
• Transcription factors
• Chromosome 11 is believed to contain a T-S gene,
  because inserting a healthy copy into a cancer
  cell will stop further tumor formation

http//www.ncbi.nlm.nih.gov/books/bv.fcgi?callbv.
View..ShowSectionridgnd.section.107
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Sources

• Lewis, Ricki. Human Genetics Concepts and
  Applications.
• Maroni, Gusavo. Molecular and Genetic Analysis of
  Human Traits.
• Wikipedia http//en.wikipedia.org/wiki/Cancer.
• Levine, A.J. Tumor Suppressor Genes, the Cell
  Cycle, and Cancer.