Question

Sol.(a) [Key Concept: Aneuploidy — 2n±1 and 2n±2] Karyotypes of 2n±1 and 2n±2 are called ANEUPLOIDY — changes in chromosome number involving addition or deletion of LESS THAN a complete set of chromosomes. 2n+1 = trisomy (e.g., Down's syndrome); 2n-1 = monosomy (e.g., Turner's syndrome); 2n+2 = tetrasomy; 2n-2 = nullisomy. Polyploidy involves addition of COMPLETE chromosome sets (2n→3n, 4n, etc.); allopolyploidy involves combining sets from different species; monosomy is specifically 2n-1.