Practice question

Human diploid complement 46 comprises 44 autosomes plus two sex chromosomes XX or XY. Monosomy reduces count one, leaving 45 total chromosomes countable on metaphase spread. Autosomal monosomy of any chromosome except perhaps small regions generally lethal early embryonically due to haploinsufficiency many genes lacking backup. Sex chromosome monosomy 45,X Turner syndrome viable because dosage compensation by X-inactivation buffers imbalance and Y genes not required for survival, though phenotype abnormal with short stature, gonadal dysgenesis, cardiovascular anomalies. Counting 45 chromosomes confirms monosomy state versus normal 46.