Final answer:
Spontaneous changes in DNA structure/sequence generally result from errors during DNA replication. These errors can lead to mutations if not corrected by repair mechanisms, resulting in changes in the DNA sequence.
Step-by-step explanation:
Spontaneous changes in DNA structure/sequence generally result from errors during DNA replication. DNA replication is a highly accurate process, but mistakes can occasionally occur, such as a DNA polymerase inserting a wrong base. If these mistakes are not corrected by repair mechanisms, they can lead to mutations.
For example, if a wrong base is inserted in the new strand of DNA during replication, this wrong base could become permanent and result in a mutation. Small changes in the DNA sequence are usually point mutations, where a single nucleotide is changed.