, Klinefelter's syndrome is a chromosomal disorder caused by the presence of an additional copy of the X-chromosome, resulting in a karyotype of 47, XXY (which consists of 44 autosomes + XXY). Colourblindness is described as a sex-linked (X-linked) recessive disorder, not Y-linked. Down syndrome is caused by the trisomy of chromosome 21 (an additional copy of chromosome 21), while the XO condition (45 chromosomes) is characteristic of Turner's syndrome.