Introduction to Human Disease: Mutagens, Carcinogens and Chemically Induced Carcinogenesis

These flashcards cover the key concepts from the lecture on mutagens, carcinogens, and chemically induced carcinogenesis.

What is a mutagen?

A mutagen is a chemical or physical phenomenon that causes changes to the composition of DNA.

Examples of physical mutagens include:

UV light, X-rays, and gamma rays.

What does the Ames test measure?

The Ames test measures a chemical's ability to induce reverse mutations in specific strains of Salmonella typhimurium.

What is a carcinogen?

A carcinogen is any substance that can lead to cancer.

What are the two types of carcinogens?

Direct carcinogens and procarcinogens.

What is chemical carcinogenesis?

The study of chemical carcinogens and their modes of action.

What is the role of DNA repair mechanisms?

DNA repair mechanisms correct mutations caused by damage to DNA.

What is the difference between direct and indirect carcinogens?

Direct carcinogens are reactive and can form DNA adducts without metabolism, while indirect carcinogens require metabolic activation.

What is an example of a direct carcinogen?

Nitrogen mustards or methyl nitrosourea are examples of direct carcinogens.

What does the term 'toxicant' refer to?

A toxicant is any substance that causes harm to a living organism.

How do toxicants enter the body?

Toxicants can enter the body through ingestion, inhalation, or skin absorption.

What is the significance of Sir Percivall Pott's work?

He reported that chimney sweeps had a higher incidence of scrotal cancer attributed to soot exposure, marking the first account of occupational cancer.

What is the consequence of the Ames test showing a positive result?

A positive result indicates that a compound is a confirmed mutagen.

Name a method used to identify relationships between chemical structure and toxicity.

Structure-activity relationship (SAR) studies.

What is cyclization and its relation to DNA damage?

Cyclization can cause undesired interactions that lead to DNA strand breaks.

How does oxidative damage occur in DNA?

Oxidative damage occurs through the formation of reactive oxygen species that modify DNA.

What is the function of DNA glycosylases in DNA repair?

DNA glycosylases remove damaged nitrogenous bases, creating an AP site.

What does base excision repair (BER) involve?

BER involves the removal of damaged bases and subsequent repair processes to restore DNA integrity.

What types of mutations can alkylating agents cause?

Alkylating agents can cause base substitutions and cross-linking leading to mutations.

What is the role of endonucleases in DNA repair?

Endonucleases cleave the phosphodiester bond within a polynucleotide chain to facilitate repair.

How can deaminating agents affect DNA?

Deaminating agents can convert bases, causing base mismatches during DNA replication.

What is the definition of carcinogenesis?

Carcinogenesis is the process through which cancer develops.

What factors influence the fate of a toxicant?

Exposure routes, metabolism, distribution, and excretion influence toxicant fate.

What is a procarcinogen?

A procarcinogen is a substance that becomes activated to form a carcinogen within the body.

Explain the concept of 'ultimate carcinogen'.

An ultimate carcinogen is a metabolite that can react with DNA to cause mutations.

How do bulky aromatic adducts form in DNA?

Bulky aromatic adducts form when DNA reacts with polycyclic aromatic hydrocarbons.

What kind of damage does UV light primarily cause to DNA?

UV light causes dimerization of pyrimidines leading to DNA distortions.

What is the main purpose of nucleotide excision repair (NER)?

NER repairs bulky DNA adducts caused by UV light and chemical exposure.

What is the significance of P53 in cancer?

P53 is a tumor suppressor protein that regulates cell division and prevents tumor formation.

What is the role of RNA polymerase in DNA repair?

RNA polymerase is not directly involved in DNA repair but plays a role in transcribing RNA from DNA segments.

List an example of an alkylating agent. 

Dimethylnitrosamine is an example of an alkylating agent.

What is the role of metabolic activation in carcinogenesis?

Metabolic activation transforms procarcinogens into active carcinogens that can damage DNA.

Describe the process of DNA adduct formation.

DNA adduct formation occurs when a chemical binds covalently to DNA, altering its structure.

What is the main consequence of improper DNA repair?

Improper DNA repair can lead to mutations, genomic instability, and cancer.

Explain the significance of K. Yamagiwa and K. J. Itchikawa's research.

Their research demonstrated that coal tar could induce cancer in animals, establishing a chemical link to carcinogenesis.

What happens during the conversion phase of carcinogenesis?

Preneoplastic cells are transformed to malignantly expressing cells.

What mechanism do direct carcinogens employ to damage DNA?

Direct carcinogens can form DNA adducts without requiring metabolic modification.

What types of agents are reactive oxygen species associated with?

Reactive oxygen species are often associated with oxidative stress and damage.

Identify one role of DNA ligase during DNA repair.

DNA ligase joins DNA fragments together by catalyzing phosphodiester bond formation.

What process is involved in the mismatch repair mechanism?

Mismatch repair involves identifying and repairing erroneous insertion, deletion, and misincorporation of base pairs.

Give an example of a toxic endpoint resulting from toxicant exposure.

Cell death or carcinogenesis are examples of toxic endpoints.

How can chronic exposure to aflatoxin B1 affect health?

Chronic exposure to aflatoxin B1 is associated with increased risks of liver cancer.

What initiates carcinogenesis?

Carcinogenesis is initiated by genetic alterations and mutations in cellular genes.

Define toxicity testing and its relevance to toxicology.

Toxicity testing evaluates the effects of toxicants in living systems to assess their potential hazards.

What is the core function of statistics in toxicology?

Statistics helps in determining the significance and risk of toxicant exposure within populations.

How is DNA polymerase involved in DNA repair mechanisms?

DNA polymerase synthesizes new DNA strands using the undamaged complementary strand as a template.

Why are controls important in the Ames test?

Controls are important to validate the test results and ensure the reliability of the findings.

What is the impact of genetic mutations on tumor suppressor genes?

Mutations in tumor suppressor genes can lead to loss of function, promoting cancer development.

Describe the process of oxidative DNA damage.

Oxidative DNA damage occurs when reactive oxygen species react with DNA, causing base modifications.