Diagram showing<unk>  formation. MI and MII are the stages of meiosis, while the blue and pink circles are male and female cells respectively, and the blue and pink bars are Y- and X-chromosomes respectively. The purple cell has 2 Y-chromosomes and 1 X-chromosome due to fusing with a male cell with 2 Y-chromosomes, which was due to division problems in MII of the male. 47,XYY is not inherited, but usually occurs as a random event during the formation of sperm cells. An incident in chromosome separation during anaphase II (of meiosis II) called nondisjunction can result in sperm cells with an extra copy of the Y-chromosome. If one of these atypical sperm cells contributes to the genetic makeup of a child, the child will have an extra Y-chromosome in each of the body's cells. In some cases, the addition of an extra Y-chromosome results from nondisjunction during cell division during a post-zygotic mitosis in early embryonic development. This can produce 46,XY/47,XYY mosaics.
XYY syndrome
Marfan syndrome
XYYY syndrome
Klinefelter syndrome
XX male syndrome
Sotos syndrome
XXXY syndrome
XYYYY syndrome