<prompt> Male downs syndrome genotype?46 XY47 XY45 XY47 XXY  <response>: Ans. is b i.e., 47 XY 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 robesonian translocation. t 13 : 21 t 14 : 21 at 15 : 21 Very rarely long arm of chromosome 21 is triplicate Paial trisomy. 