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Questions and Answers
What is the primary characteristic of cancer cells compared to typical cells?
What is the primary characteristic of cancer cells compared to typical cells?
Which type of tumor is characterized as being non-invasive with the potential to become malignant?
Which type of tumor is characterized as being non-invasive with the potential to become malignant?
Which of the following statements is true regarding mutagens and carcinogens?
Which of the following statements is true regarding mutagens and carcinogens?
What is a point mutation?
What is a point mutation?
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What is the purpose of the Ames Test in mutagen screening?
What is the purpose of the Ames Test in mutagen screening?
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Which of the following exposures is commonly associated with genotoxic effects?
Which of the following exposures is commonly associated with genotoxic effects?
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What is a common source of Polycyclic aromatic hydrocarbons (PAHs)?
What is a common source of Polycyclic aromatic hydrocarbons (PAHs)?
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What temperature is associated with significant HCA formation when cooking meats on a flame BBQ?
What temperature is associated with significant HCA formation when cooking meats on a flame BBQ?
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Which of these compounds is produced from the cooking process of animal tissue above 180 degrees Celsius?
Which of these compounds is produced from the cooking process of animal tissue above 180 degrees Celsius?
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Which of the following compounds is known to be a common carcinogen produced from high temperature cooking of starchy foods?
Which of the following compounds is known to be a common carcinogen produced from high temperature cooking of starchy foods?
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Which type of compound is Thalidomide classified as?
Which type of compound is Thalidomide classified as?
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What is the role of cytochrome P450 enzymes in the context of bioactivation?
What is the role of cytochrome P450 enzymes in the context of bioactivation?
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In cancer progression, what percentage of recurrence cases shows cells that appear normal before becoming cancerous again?
In cancer progression, what percentage of recurrence cases shows cells that appear normal before becoming cancerous again?
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Which gene is primarily associated with apoptosis in cancer development?
Which gene is primarily associated with apoptosis in cancer development?
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What is the final step in the sequence of gene loss typically observed in cancer development?
What is the final step in the sequence of gene loss typically observed in cancer development?
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Which statement about cancer is accurate given the context of molecular patterns in cancer?
Which statement about cancer is accurate given the context of molecular patterns in cancer?
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Study Notes
Overview of Cancer
- Cancer is a general term for over 100 diseases, characterized by abnormal and uncontrolled cell growth.
- Cancer cells are not immortal.
- Normal cells typically live about 40 generations. Afterwards, they accumulate excessive genetic errors, leading to death.
- Cancerous cells live longer, increasing the probability of accumulating errors.
Cancer Terms
- Benign tumor: A non-invasive growth that has the potential to become malignant.
- Malignant tumor: A cancerous growth that spreads to other parts of the body through the bloodstream or lymph nodes.
Mutagens vs. Carcinogens
- Mutagens are substances that cause alterations in genetic (DNA) material.
- Cancer requires a mutation, but a mutation doesn't always result in cancer.
Types of Mutations
- Point Mutations: Replacement of one nucleotide with another. Some point mutations have no effect, while others can alter the protein's function.
- Frameshift Mutations: Deletion of one or more nucleotides, causing the reading frame to shift and change the amino acid sequence. This usually leads to a non-functional protein.
Other Types of Mutations
- Chromosome deletions: Loss of a segment of a chromosome.
- Thymine dimers: Formation of abnormal bonds between adjacent thymine bases in DNA, often caused by UV light.
- Strand breaks: Damage to the DNA strand, often caused by ionizing radiation (e.g., X-rays).
- DNA adducts: Formation of a chemical group (adduct) on a DNA base, often caused by carcinogens.
- Oxidized base: A base modified by oxidation, often caused by oxidizing agents.
Carcinogens
- Carcinogens are compounds that induce severe DNA mutations, leading to cancer.
Mutagen Screening: Ames Test
- The Ames test uses Salmonella typhimurium bacteria to screen for potential mutagens.
- In the test, bacteria are exposed to the suspected mutagen and grown on a growth medium lacking the amino acid histidine.
- If bacteria grow, it indicates that the compound can reverse the mutation and is a mutagen.
Common Exposures to Mutagens and Carcinogens
- Polycyclic aromatic hydrocarbons (PAHs): Found in fossil fuel combustion and some foods (processed meats).
- Creosote-soaked wood: Found in some forms of treated wood.
- Nitrosamines: Found in processed foods and cigarette smoke.
- Saliva: Can affect the cooking process to produce carcinogens.
Common Carcinogenic Exposures
- Benzo[a]pyrene (PAH): Results from incomplete combustion of organic compounds (in cigarette smoke, car exhaust, forest fires).
Common Genotoxic Exposures
- Heterocyclic amines (HCAs): Produced during high-temperature cooking of animal proteins (meat cooking processes like barbecuing). Higher temperatures produce more HCAs.
- Acrylamide: Formed during high-temperature cooking of starchy foods (e.g., french fries, potato chips).
Alcohol and Smoking (Synergistic Effect)
- Alcohol dissolves fats in cell membranes.
- Carcinogens in smoke enter cells more easily after alcohol exposure, increasing the potential for damage.
Bioactivation
- Compounds become more toxic after being metabolized.
- Benzo[a]pyrene metabolism via CYP450 enzymes in Phase I and II reactions can cause DNA damage.
Bioactivation Mutagenicity Test
- This test determines if a compound's mutagenic effects are increased (or not) after bioactivation by liver enzymes (like CYP450).
Teratogens
- Teratogens are compounds that only cause birth defects in a developing fetus
- Thalidomide is a famous example, used as a sedative in pregnant women but caused severe birth defects.
Molecular Cancer Progression Model
- This model shows the DNA changes that lead to cancer, from precancerous to full-blown cancer and eventually metastasis.
Clinical Cancer Progression Model
- This model describes how cancer progresses from precancerous to cancerous stages, considering clinical and animal data, focusing on cellular and tissue morphology and growth rates.
Clinical Cancer Patterns
- Cancer can recur after surgical removal.
- In some cases, cells appear to be normal but transform suddenly.
Molecular Patterns in Cancer
- Cancer develops from multiple gene mutations, including those related to:
- DNA repair
- Anchorage dependence
- Growth suppressors
- Growth promoters
- P53 (apoptosis gene)
Patterns of Cancer
- Multiple gene loss combinations can lead to cancer.
- Cancers in the same tissue can have different molecular causes, making a universal cure challenging
Environmental Toxicologists: Cancer Models
- These models show the stages in the induction of cancer by carcinogens in animal experiments.
Initiation
- Initiation creates a neoplastic cell, permanent DNA changes.
- Chemical exposure alters DNA via mutations..
- DNA repair and apoptosis are part of this process.
Promotion
- The neoplastic cell grows. This process can take time.
- Repeated exposures promote cell growth, leading to dysplasias.
- Benign tumors can develop and evolve.
- DNA repair mechanisms are often damaged in the early stages of promotion.
Progression
- Visible tumors emerge.
- Genetic changes continue, altering the surrounding tissues.
- Cancer cells can spread to other parts of the body—metastasize.
- Cells lose communication with each other.
Problems with Cancer Research
- Long latency periods (10-20 years).
- No safe doses for research studies
- It is complex to satisfy all cancer research models.
- Separating cure vs prevention.
USA and China Cancer Data
- Cancer incidence rates vary within and between nations. (USA and China shown in graphs).
Cure vs. Prevention
- Some possible preventable cancer deaths are highlighted (76%) are potentially preventable, with diet, smoking, reproductive factors, alcohol consumption, food additives, and industrial pollutants all listed as contributors.
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Description
This quiz covers essential concepts related to cancer, including definitions of benign and malignant tumors, and the distinction between mutagens and carcinogens. Explore the types of mutations involved in cancer development, and understand the biology behind cell growth and cancer formation.
