Which Ethical Standpoint Is The Catholic Church's Teaching On Embryo Research Based?

The Catholic position on the issue is mainly based on a 'Natural Law' approach to ethics. Catholics believe that humans are made in the image and likeness of God and that all human life is sacred. God's creation is good and what He makes is seen to be holy and sacred. Therefore, the Church can never justify the practice of human beings being created by artificial means. The late Pope John Paul II stated that, 'From the time the ovum is fertilised, a life has begun which is neither that of the father or the mother-it is rather a life of a new human being with his/her growth.' The arguments included in this quote can be backed up by St. Paul's letter to the Corinthians where he states ' You are not your own' (6:19).  

Many Catholics and indeed some other Christians support this view that life begins at conception and the only way a life can be created is by natural fertilisation. This theory is also backed up by the official Catholic Church's teaching on the sanctity of the human embryo. 'Human life must be respected and protected absolutely from the moment of conception.'

Is preimplantation genetic diagnosis and the discarding of affected embryos morally equivalent to prenatal diagnosis and selective abortion?