Well certain disorders are found on certain chromosomes and on certain parts of the chromosome. How they find out how, i don't know. But if some pieces of a specific chromosome they can predict they will have a certain disorder
One method involves the CHORIONIC VILLI SAMPLING where the geneticist does exactly that. They take a sample from the embryo's outermost extra-embryonic membrane, the chorion, that forms villi which...
IDDM is still idiopathic although the the most likely cause of Type I diabetes is immune sequel. Antibodies that were activated against a viral infection are also capable of crossreacting with...