Using specific examples, distinguish between those mutations that are spontaneous and those that are the result of exposure to substances or radiation. How might some of the mutagenic substances be used in cellular biology and medicine?
What will be an ideal response?
Answer: Spontaneous mutations are those that are intrinsic to the DNA itself and include mismatching due to tautomeric shifts, deamination, and depurination. Induced mutations are due to exogenous chemicals or radiation. Examples include pyrimidine dimers, frameshift mutations, and double-stranded DNA breaks. In cellular biology, ethidium bromide (an intercalating agent) has been used to allow us to visualize nucleic acids in gel electrophoresis and to intentionally induce mutations. Base analogues are used to treat cancer by disrupting DNA replication and causing lethal mutations to arrest the growth of fast-growing cells.
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