**Core Concept**
A point mutation is a type of genetic mutation that occurs when a single nucleotide base is altered in a DNA sequence, resulting in a change in the amino acid sequence of a protein. This can have significant effects on protein function and can lead to various diseases. Point mutations can be classified into different types, such as missense, nonsense, frameshift, and silent mutations.

**Why the Correct Answer is Right**
Point mutations are caused by changes in a single nucleotide base, which can lead to changes in the amino acid sequence of a protein. For example, a missense mutation can result in the substitution of one amino acid for another, leading to a change in protein function. This can have significant effects on the protein's structure and function, leading to various diseases. In contrast, other types of mutations, such as deletions or insertions, involve the addition or removal of nucleotides, leading to changes in the protein sequence.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because deletions involve the removal of nucleotides, leading to changes in the protein sequence, but are not typically caused by point mutations.
* **Option B:** This option is incorrect because insertions involve the addition of nucleotides, leading to changes in the protein sequence, but are not typically caused by point mutations.
* **Option C:** This option is incorrect because chromosomal mutations involve changes in the number or structure of chromosomes, which is a different type of genetic mutation.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that point mutations can have significant effects on protein function, leading to various diseases. Understanding the types of genetic mutations and their effects on protein function is crucial for diagnosis and treatment.

**Correct Answer:** D.