Research in molecular genetics has made great advances in recent years that have wide practical applications. At the same time, it has been confirmed that not everything provided by modern genetic research is good and beneficial for humans. In particular, the discovery of the CRISPR/CAS9 method has made it possible to interfere very effectively with an individual’s hereditary characteristics, which has forced doctors, lawyers, ethicists, sociologists, theologians and representatives of churches to take a clear stance on the issue. The need for further scientific development requires the limits of research to be defined in order to avoid irreparable damage to the gene pool of humanity. The aim of this article is to examine the Magisterium of the Catholic Church in dealing with current bioethical issues arising from new scientific discoveries and to present Christian principles in the context of the possibilities offered by molecular editing using CRISPR/CAS9. The position of the Catholic Church on current developments in the field of biomedicine, even at a time of significant biomedical discoveries, is based on a holistic view on human life, its value and mission. In the deepest sense of the word, gene therapy should be a therapy for a specific disease of a given organism that respects the integral good of the human person. Clinical interventions aimed at improving the genome of an individual, and therefore of society, are unacceptable. Human life must not become the object of a eugenic positivist-materialist mentality. The teaching office of the Church promotes scientific development for the common good of humanity and, at the same time, strives to preserve the dignity and integrity of every human being.

Stem cells exist and can do a lot. For several decades, bone marrow and umbilical cord blood transplants containing haematopoietic stem cells have been used in the treatment of blood diseases. Genetic modifications (gene therapy) of such cells help to cure complex immunodeficiencies and severe anaemias. The limbal stem cells taken from the eye and properly multiplied can regenerate the damaged cornea, and the epidermal stem cells help in the treatment of severe burns and some hereditary, severe skin diseases. Promising experimental research is under way on other uses of stem cells. However, these cells are appropriately selected, having real ability to differentiate into specialized cells whose malfunction is the cause of the disease. Therapeutic applications of stem cells are apparently limited to date. Meanwhile, the Internet is full of advertisements for supposedly miraculous treatments for almost any disease. Stem cells have become a modern synonym of the Holy Grail. A wonderful dish, transforming every drink into elixir of health, youth and long life. Stem cells from a single source, e.g., umbilical cord blood, or so-called cells, although without proven properties of stem cells, are offered in commercial private clinics as a panacea for autism, cerebral palsy, spina bifida, eye diseases, amyotrophic lateral sclerosis and dozens other disorders. Without justification for their action in these diseases, without convincing evidence of safety, but for a high fee. This article discusses stem cells and misunderstandings about including any cells among them. It draws attention to the real possibilities and confirmed uses of stem cells and presents the problems, doubts and dangers for patients associated with commercial offers of treatments using “stem” cells. The author cites the positions of scientific institutions and societies warning against premature commercialization of unjustified and potentially dangerous therapies.