Cancer Genetics Lecture Review

Cancer Characteristics

• Cancer is characterized by uncontrolled cell division.
• It is a genetic disease at the cellular level.
• Over 100 types of human cancers are recognized.

Cancer Development

• Cancers arise from mutations in critical genes, leading to unregulated cell proliferation.
• Malignant cells are invasive and can metastasize to other body parts.
• Tumors form due to rapidly dividing cells stacking up.

Genes Involved in Cancer

• Gene P: Mutant forms involved in cancer; its function is to kill cells with chromosome damage.
  • Likely a tumor suppressor gene (recessive-acting: excessive proliferation in homozygous mutants).
• Gene M: Mutant forms involved in cancer; signals for cell division during healing.
  • Likely a proto-oncogene (dominant-acting: excessive proliferation in heterozygous mutants).

Tumor Suppressor Genes

• Prevent excess cell proliferation during normal cell division.
• Cancer arises when there is insufficient gene product activity.

Specific Cancer Examples

• Retinoblastoma (RB1): Rare childhood retinal cancer, associated with mutations in both alleles of the Rb gene as per Knudson's model.
• BRCA1: Involved in double-strand DNA break repair; mutations increase cancer risk.
  • Dominant at the organismal level, but recessive at the cellular level (mutant or loss of function alleles).