With new genetic diagnostic and therapeutic capabilities come many controversies about how they should be used. For example, there are concerns that genetic information might be used improperly to discriminate (eg, by denying health insurance coverage or employment) against people with genetic risk factors for particular disorders. Issues include the privacy of a person’s own genetic information and the question of whether testing should be compulsory.
Prenatal screening for genetic abnormalities that cause serious disorders is widely supported; however, there is concern that screening could also be used to select for traits that are aesthetically desirable (eg, physical appearance, intelligence).
Cloning is highly controversial. Animal studies suggest cloning is much more likely than natural methods to result in defects that are lethal or cause serious health problems. Creating a human by cloning is widely seen as unethical, is illegal in most jurisdictions, and is technically difficult.
Inheritance of certain mitochondrial disorders has now been prevented by creating an embryo using biological material from 3 different people. Techniques are based on the fact that mitochondria are derived entirely from the mother and that mitochondria contain their own DNA separate from nuclear DNA.
In pronuclear transfer, a woman with a mitochondrial mutation has an egg fertilized in vitro with sperm from her partner. A donor egg from a woman with normal mitochondria is also fertilized with sperm from the same donor. Then the male and female pronuclei are removed from the first zygote and transplanted into the donor zygote after its nucleus has been removed. This fertilized embryo thus contains the sperm DNA from a male, the ovum DNA from the affected female, and the normal mitochondria (and their genome) from a second female, resulting in an embryo without mitochondrial disease.
Maternal spindle transfer is a similar procedure. In this case, an oocyte is removed from the affected woman. When the oocyte is in the metaphase II stage of cell division, the spindle–chromosome complex is removed and inserted into a healthy donor oocyte from which the nucleus has already been removed. This egg is then fertilized with sperm and implanted in the recipient
