Practice question

Variation concerning individual chromosome gain or loss while maintaining most diploid complement termed aneuploidy distinct from euploidy involving whole sets. Aneuploidy subdivided hypoploid forms monosomy 2n-1 and nullisomy 2n-2 versus hyperploid forms trisomy 2n+1 and tetrasomy. Origin predominantly meiotic nondisjunction where homologs or sister chromatids fail to separate due spindle defects, producing n+1 and n-1 gametes. Phenotypically often deleterious due to unbalanced gene dosage disrupting regulatory networks. Many cases embryonic lethal except sex chromosome aneuploidies and small autosomes like 21 that tolerate dosage imbalance partially.