Mutations

·  Depurination: Loss of a purine base (adenine or guanine), leading to an apurinic site. This can be repaired by base excision repair.

·  Deamination: Converts cytosine to uracil or adenine to hypoxanthine, causing mispairing. Repaired by base excision repair.

·  Free Radicals/Oxidative Damage: Oxidative stress can modify bases, like turning guanine into 8-oxoguanine, which pairs incorrectly. Repaired by base excision repair. Free Radicals indirectly/directly affect DNA by altering purines and pyrimidines, breaking phosphodiester bonds, and producing deletions, translocations, and fragmentation.

·  Ionizing Radiation: X-rays and gamma rays can break DNA strands, repaired by non-homologous end-joining (NHEJ) or homologous recombination.

·  UV Light: Creates pyrimidine dimers, disrupting DNA structure, repaired by nucleotide excision repair.

·       Explain what are mutagens are, including the following classes: base analogs, alkylating agents, intercalating agents, adduct-forming agents

Mutagens: Natural or artificial agents that induce mutations

·  Base Analogs: Mimic normal bases but pair incorrectly (e.g., 5-bromouracil). They increase tautomeric shifts

·  Alkylating Agents: Add alkyl groups to bases, causing mispairing or strand breaks. Transition mutations result from them.

·  Intercalating Agents: Insert between DNA bases, causing frameshifts (e.g., ethidium bromide). Can also cause DNA unwinding and base-pair distortions

·  Adduct-Forming Agents: Bind to DNA and covalently binds to DNS, altering conformation and interfering with replication and repair to cause mutations.