A disease caused by an autosomal primary non-disjunction is
(1) Down's syndrone
(2) Kilnerfelter's syndrome
(3) Turner's syndrome
(4) Sickle-cell anemia
(1) Non-disjunction is the failure of chromosomes to disjoin or separate and move away to opposite poles. Non-disjunction of 21st chromosome during oogenesis is the cause of down's syndrome. It occurs due to the presence of an additional copy of chromosome no 21 (trisomy of 21 chromosome) in humans.