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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.