Why is karyotyping most useful for finding large chromosome changes?

Karyotyping is most useful for identifying large chromosomal changes because of its limited resolution compared to modern molecular techniques. In a standard karyotype, chromosomes are stained to produce approximately 400 visible bands, with each band potentially containing hundreds of genes.12

Because this method relies on visual inspection of condensed chromosomes during mitosis, it is primarily effective at detecting large-scale aberrations, such as aneuploidy (abnormal chromosome number) or significant structural rearrangements like large deletions, duplications, inversions, and translocations.12

In contrast, smaller genetic defects—such as those involving only a few genes or single-base-pair changes—are often too small to be visualized through traditional staining. For these smaller mutations, more sensitive DNA tests like FISH, CGH, or PCR are required, as they can detect changes at a much higher resolution.3