Practice question

Chromosome variations divide into numerical and structural classes. Numerical includes aneuploidy and polyploidy where whole set number changes, arising from nondisjunction or spindle failure. Structural rearrangements keep chromosome number constant but alter linkage arrangement: deletions removing segments, duplications repeating segments, inversions reversing orientation, and translocations moving segments between non-homologs. Polyploidy therefore does not belong to structural category. Inversions and translocations preserve total DNA content but change gene order, while deletions and duplications change dosage. Distinction matters for pairing behavior, recombination suppression, and phenotypic severity assessment.