question about DS and twins

[CrushWithEyeliner]

I was wondering if it was possible to have twins whereby one had downs syndrome and the other not. Sorry if this is ignorant of me I know, but tis a genuine question.

As Down's Syndrome is caused by a chromosomal defect, and fraternal twins are genetically distinct, I would have thought it quite possible for one twin to have Down's and the other not, so long as they are not identical. However, I've never come across an example of it in RL.

ah i see thank you ew