<prompt> Male downs syndrome genotype-46 XY47 XY45 XY47 XXY  <response>: Ans. is b i.e., 47 XY 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.4 have robertsonian translocation, n t13 : 21t14 : 21t15 : 21Very rarely long arm of chromosome 21 is triplicate Partial trisomy. 