Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
Gene therapy is permissible, whether by transferring all or parts of genes, repairing them, or silencing them, provided that it does not lead to the mixing of lineages, and that the intention is treatment and not changing the creation of Allah.
Answering your question, The Assembly of Muslim Jurists of America, states:
Gene therapy is permissible, whether by transferring all or parts of genes, repairing them, or silencing them, provided that it does not lead to the mixing of lineages, and that the intention is treatment and not changing the creation of Allah, along with protecting the privacy of individuals undergoing this treatment, safeguarding all their rights, and not discriminating against them.
Some genetic diseases can be considered among the defects that jurists have mentioned as justifying the separation between spouses, provided that the conditions are met for these diseases to share the same rationale as their jurisprudential counterparts, in the absence of impediments. This applies when such diseases were unknown at the time of the marriage contract, there is no indication of acceptance of these diseases afterwards, there is no available treatment to alleviate the diseases, and especially when there is a likelihood of transmitting serious diseases to offspring.
Genetic counseling for families or those planning to marry is in line with the principles of Shari`ah that encourage treatment and prevention of disease. It should be encouraged without being mandatory, especially for families with members suffering from hereditary diseases, while ensuring the protection of the privacy of individuals undergoing such tests, their rights, and no discrimination against them.
In the treatment of genetic diseases, if it is impossible to select a sperm or egg from the couple that does not carry the diseased gene, then replacing one of them with what is called a “donor cell” is absolutely prohibited due to the resulting mixing of lineages.
It is encouraged for decision-making bodies in countries to enact laws that assist individuals with genetic diseases and those with special needs, and to provide support for them in various fields, including efforts to integrate them into society and create suitable conditions for this purpose.
Read also:
Genetic Disorders: Islamic View
Is Genetic Engineering Allowed in Islam?
Must I Reveal Physical Defects before Marriage?
Am I Required to Reveal Possible Health Problem to Suitor?
Almighty Allah knows best.
Source: AMJA Online