WIKIMEDIA, SCIENCEGENETICSWhen a couple has a child with a genetic disorder, they often ask how likely they are to pass the disorder on to another child. To determine the risk of this happening, clinicians must figure out when the disorder-associated mutation arose: Did it spring up de novo during the creation of the sperm or egg that contributed to the child’s genetic makeup, or did already-present genetic abnormalities in the parents form a causative combination?
There is also a third possibility: one parent might harbor some abnormal cells derived from mutations that arose early on during his or her own life. These mutations may not have obvious health effects and can go unnoticed in most genetic screens. Researchers have long recognized this possibility, but a paper published today (July 31) in The American Journal of Human Genetics attempts to better quantify the phenomenon of mosaicism.
The authors used extra-sensitive molecular methods to analyze the blood of 100 couples who have children with disorders caused by DNA deletions, all of which were initially determined to be de novo. But with the more rigorous blood test, members of four of the couples were found to have the same mutations as their children, ...
