Gene therapy is a medical field that focuses on the replacement of faulty genes with healthy ones to treat or prevent genetic disorders.

Somatic cell gene therapy replaces mutant alleles with healthy alleles in affected somatic (body) cells to treat diseases.

Somatic cells have a limited lifespan and are replaced by stem cells with the original faulty allele.

Somatic gene therapy only affects body cells and does not affect germ cells (egg cells and sperm cells).

This means that germ cells would still contain the faulty allele, so it can still be inherited by offspring.

Germline cell gene therapy involves inserting a healthy allele into germ cells or embryos to prevent genetic diseases from birth.

1. The rights of the unborn child are violated, as they cannot provide consent.
2. It causes irreversible changes, the long-term outcomes of which are not fully understood.
3. It could be used for non-therapeutic enhancements, such as selecting desirable traits.

As a result, germline cell gene therapy is illegal for humans in most countries.

The healthy allele can be obtained by removing it from healthy cells or synthesising it in the laboratory.

Engineered plasmids, such as in viral vectors, are used to deliver healthy alleles into the nucleus of affected somatic cells.

1. Delivering healthy alleles to cells
2. Getting healthy alleles into the nucleus
3. Maintaining the expression of healthy alleles