What is defined as a change in chromosome structure that results in new gene combinations?

A change in chromosome structure that results in new gene combinations is best described as a chromosomal mutation. These mutations involve larger segments of DNA than point mutations or frameshift mutations and can include duplications, deletions, inversions, or translocations of chromosome segments.

Chromosomal mutations can significantly impact genetic diversity by rearranging the existing genes or changing the regulatory elements that control gene expression. Such changes can lead to new traits in organisms, which can be subject to natural selection, thereby influencing evolution.

In contrast, frameshift and point mutations involve alterations to individual nucleotides, which can affect gene function but do not typically result in large-scale changes to the chromosome structure or create new gene combinations. Nonsense mutations, a type of point mutation, specifically introduce a premature stop codon, leading to incomplete proteins, further illustrating that they do not provide the same level of structural change as chromosomal mutations.