Inversion mutations are a specific type of chromosomal mutation where a segment of the chromosome breaks off, rotates 180 degrees, and then reattaches to the same chromosome. This process can disrupt the normal gene order, potentially leading to significant changes in the organism's phenotype. Unlike neutral mutations, which do not affect the organism's fitness, or substitution mutations, which involve the replacement of one nucleotide with another, inversion mutations can have widespread effects on gene expression and function due to the rearrangement of genetic material.