**Core Concept**
A point mutation is a type of genetic mutation where a single nucleotide base is altered in a DNA sequence. This change can result in the substitution of one amino acid for another, leading to changes in protein function.

**Why the Correct Answer is Right**
Point mutations can be further classified into three types: transitions (purine to purine or pyrimidine to pyrimidine), transversions (purine to pyrimidine or vice versa), and insertions or deletions (indels). The correct answer will not fit into any of these categories.

**Why Each Wrong Option is Incorrect**
* **Option A:** Frameshift mutations, which result from insertions or deletions of nucleotides, are a type of point mutation. These changes can significantly alter the amino acid sequence and protein function.
* **Option B:** Nonsense mutations, which are point mutations that result in a premature stop codon, are a type of point mutation. These mutations can lead to the production of truncated proteins or no protein at all.
* **Option C:** Missense mutations, which are point mutations that result in the substitution of one amino acid for another, are a type of point mutation. These mutations can lead to changes in protein function.

**Clinical Pearl / High-Yield Fact**
In genetic testing, point mutations can be identified through techniques such as PCR (polymerase chain reaction) and Sanger sequencing. These methods can help clinicians diagnose genetic disorders and predict the likelihood of disease inheritance.

**Correct Answer: D. Frameshift mutations are a type of point mutation that result from insertions or deletions of nucleotides.**