Down syndrome - all are seen except -: (A) t (14; 21), (B) t (11: 14), (C) Trisomy 21, (D) t (15: 21)
Answer is B. Ans. is 'b' i.e., t (11: 14) o In 95% of cases of Down syndrome-trisomy of 21:-Extra chromosome is of maternal in origin.1% have mosaic with some all have 46 chromosome, a 4% have robertsonian translocation.t (13 : 21)t (14 : 21)t (15 : 21)o Very rarely tong arm of chromosome 21 is triplicate (Partial trisomy).