Mutation and DNA Repair in Cancer

Mutation, DNA Repair, Cancer

• Mutations are heritable changes in DNA sequence, fundamental to evolution
• Mutations are sources of variation for natural selection, potentially harmful, beneficial, or silent
• Types of mutations include base substitutions (e.g., changing one nucleotide for another) and frame shifts (shifting the reading frame of the DNA)
• Consequence of point mutations can be silent (no change in polypeptide), missense (changes one amino acid), nonsense (shortens polypeptide) or frameshift (different amino acid sequence)
• Mutations outside coding sequences can alter transcription rate by affecting promoters, potentially enhancing or inhibiting transcription
• Germ-line mutations occur in gametes (sperm or egg) and are heritable; somatic mutations occur in body cells and are not heritable
• Mutations often result from spontaneous errors during DNA replication or exposure to mutagens
• Spontaneous mutations can include errors in DNA replication, reactive metabolic products, changes in nucleotide structure, and transposons
• Induced mutations arise from chemical agents (e.g., benzo(a)pyrene) or physical agents (e.g., UV light, X-rays) that damage DNA
• DNA repair mechanisms exist to detect and correct mutations minimizing damage
• Direct repair corrects incorrect structures directly; base excision and nucleotide excision repair remove abnormal parts of the strand; mismatch repair repairs base pair mismatches
• Cancer is a disease of multicellular organisms characterized by uncontrolled cell division
• Cancers originate from a single cell that mutates and grows abnormally
• A tumor is an overgrowth of cells, potentially benign or malignant
• Oncogenes are mutated genes for cell growth signaling proteins, leading to permanent activation of cell division pathways
• Proto-oncogenes are normal cell division control genes that can become oncogenes if mutated
• Tumor suppressor genes are inhibitors of cell division, preventing uncontrolled proliferation; mutations in these genes can interfere with cell division control leading to cancer

Explore the critical concepts of mutations, their types, and their implications in DNA repair and cancer biology. This quiz delves into the consequences of genetic changes, including germ-line and somatic mutations, and their impact on evolution and natural selection. Test your knowledge on how mutations can be both harmful and beneficial.