What is the result when the gene order on a chromosome is inverted?

When the gene order on a chromosome is inverted, the specific type of mutation that occurs is known as an inversion mutation. This involves a segment of the chromosome being reversed end to end, which alters the linear order of the genes on that chromosome.

Inversion mutations can impact gene expression and function depending on the location of the genes involved and whether any essential regulatory sequences have been displaced. Unlike other types of mutations, such as point mutations (which involve a change in a single nucleotide), frame shift mutations (which result from insertions or deletions that change the reading frame of the genetic code), and translocation mutations (which involve the transfer of a fragment of one chromosome to another chromosome), inversions specifically pertain to the reordering of existing genetic material without adding or removing DNA segments. This is why the correct choice is identified as an inversion mutation.