Human Fertilisation and Embryology Bill [Lords]

Does not bone marrow biopsy already take place? The point has been made that that is not with the informed consent of the child, but it could not be because a child is not of legal majority. None the less, such procedures already take place to try to help a sibling, so what is the difference in principle? If a child were created partly for that purpose—it would also be because they were wanted—that bone marrow could not be removed for at least a year after they were born, so what is the difference from existing procedure?