Male downs syndrome genotype-
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 t(13 : 21)t(14 : 21)t(15 : 21)Very rarely long arm of chromosome 21 is triplicate (Partial trisomy).
46 XY
47 XY
45 XY
47 XXY
Genetics of Common Disorders