Genetic Inheritance and Cancer Biology Flashcards

Genetic Inheritance Patterns

• Single-Gene Disorders and Twin Concordance
  • Monozygotic twins: share 100% of genes; concordance for single-gene disorder ideally 100%.
  • Dizygotic twins: share ~50% of genes; concordance for recessive single-gene disorders typically ~25%.

Identifying Genetic Causes of Diseases

• Onset age: specific age can suggest a genetic cause.
• Antibiotics: diseases cured are typically infectious, not genetic.
• Environmental Influence: diseases occurring equally in similar environments suggest a genetic basis.

Pedigree Analysis and Inheritance Patterns

• Autosomal Recessive: 25% of offspring affected from two unaffected heterozygous parents.
• Autosomal Dominant: affected individuals in every generation; recessive traits can skip generations.
• Recessive Inheritance: unaffected parents can have affected offspring.
• X-Linked Recessive: higher prevalence in males due to single X chromosome.

Cancer Biology and Genetic Mutations

• Tumor Suppressors and Oncogenes

  • Tumor suppressor genes: inhibit cell cycle progression (BRAKE PEDALS).
  • Oncogenes: promote cell cycle progression (GAS PEDAL) leading to uncontrolled cell growth.
  • Oncogenes: mutations often result in gain-of-function.
  • Tumor suppressor genes: mutations typically lead to loss-of-function.

• Dominant Negative Mutation

  • Mutant gene product interferes with wild-type gene function.
  • Single mutant allele is sufficient to cause the disease (dominant phenotype).
  • Occurs in tumor suppressor genes (e.g., p53).

• Haploinsufficiency

  • Single copy of a functional gene is insufficient to produce a normal phenotype.
  • Individual may exhibit disease even with one working copy of the gene.

Characteristics of Oncogenes

• Oncogenic Ras: decreased GTPase activity leads to prolonged signaling/increased cell proliferation.
• Amplifications of oncogenes: can lead to overexpression.

Apoptosis and Cancer

• Caspases: enzymes crucial in apoptosis (programmed cell death).
• Disruption of apoptosis is often seen in cancer.

Epigenetics and Cancer

• Epigenetic changes: alter gene expression without changing DNA sequence.
• Mechanisms: DNA methylation and histone modifications (acetylation, methylation, phosphorylation).
• Factors: environmental influences, diet, and lifestyle can lead to epigenetic modifications.

Viruses Associated with Cancer

• Viruses: Hepatitis B virus and Papillomavirus can contribute to cancer development.
• Rous sarcoma virus: induces cancer in animals, providing insights into viral oncogenesis.