De novo mutation
A mutation that is ‘new’ and not found in the parents’ blood sample. The mutation can occur in a parent’s germ cell that will go on to fertilize and result in an embryo that now carries the mutation. Alternatively, the mutation can occur early on in the fertilized oocyte. In either case, every cell in the embryo will carry the mutation. If the mutation happens once there are more cells present, there will be two cell lines, one originating from the cell with the mutation and the other originating from the cell without the mutation – a situation referred to as mosaicism.
