How do synonymous mutations differ from nonsynonymous mutations?

Synonymous mutations are a type of genetic mutation that occurs when a change in the DNA sequence does not alter the amino acid sequence of the resulting protein. This is possible due to the redundancy in the genetic code, where multiple codons can code for the same amino acid. As a result, synonymous mutations do not lead to changes in the structure or function of the protein, making them generally neutral in regard to the organism's phenotype.

In contrast, nonsynonymous mutations result in a change in the amino acid sequence, which can affect the folding, stability, and overall function of the protein. This distinction is crucial in understanding how genetic variations can influence both the evolutionary pathway of species and potential disease processes.

The other choices pertain to misunderstandings of these mutation types. Synonymous mutations do not change amino acids, while nonsynonymous mutations are specifically defined by their ability to alter the protein structure. The occurrence of nonsynonymous mutations is not restricted to DNA alone; they can be found in any part of the genetic sequence that encodes proteins, including RNA once it's transcribed.