Will a fetus survive with trisomy of the 21st chromosome (as in down's syndrome) and also with trisomy of say the 9th chromosome (which as stated by wikipedia will give a viable fetus)? Basically I am asking if a fetus will survive with 2 or more genetic defects?
Yes, the fetus will survive with the genetic defects, but the child born would have both the disorders and it would be difficult for him/her to survive.