Gene Therapy
This lesson covers:
- Using gene therapy to treat genetic disorders
- Somatic and germline gene therapy
- Ethical considerations of gene therapy
Using gene therapy to treat genetic disorders
Gene therapy is a medical field that focuses on the replacement of faulty genes with healthy ones to treat or prevent genetic disorders.
How gene therapy can treat genetic disorders:
- Identify the abnormal gene responsible for the disorder.
- Engineer a normal, functional version of this gene by removing it from healthy cells or synthesising it in the laboratory.
- Deliver the normal allele to the nuclei of target cells using a vector.
- Ensure that the gene is successfully integrated into the cells' DNA and expressed correctly.
Main approaches to using gene therapy
There are two main approaches to using gene therapy for treating or preventing genetic disorders. The method that is used depends on whether the disorder is caused by a dominant or recessive allele,
- Counteracting recessive disorders
- Add functional dominant alleles.
- This silences non-functional recessive alleles.
- Silencing faulty dominant alleles
- Insert DNA sequences that inactivate harmful dominant alleles.
- This prevents the dominant allele from functioning properly, preventing it from causing harm.
Vectors such as viruses, plasmids, or liposomes are employed to deliver DNA into the cells in both scenarios.
Somatic and germline gene therapy
Gene therapy is categorised into two types based on the cells it targets.
| Somatic gene therapy | Germline gene therapy | |
|---|---|---|
| Definition | Replaces mutant alleles with healthy alleles in affected somatic (body) cells to treat diseases. | Involves inserting a healthy allele into germ cells or embryos to prevent genetic diseases from birth. |
| Target cells for gene editing | Alters somatic cells, especially those most affected by the disorder, such as lung cells in cystic fibrosis. | Alters germ cells (egg and sperm cells) or embryos. |
| Tissues or organs affected | Impacts specific tissues and organs only. | Influences all cells within the body when inherited. |
| Inheritance | Genetic modifications are not inherited by offspring. | Modifications can be passed down to future generations. |
The healthy allele can be obtained by removing it from healthy cells or synthesising it in the laboratory.
Ethical considerations of gene therapy
Despite the potential of gene therapy to treat serious genetic diseases, it raises significant ethical questions.
| Ethical benefits of gene therapy | General ethical issues and risks of gene therapy | Issues with somatic gene therapy | Issues with germline gene therapy |
|---|---|---|---|
| Extends lives by treating diseases. | Potential misuse for enhancing aesthetic attributes rather than for medical needs. | Delivering healthy alleles to cells is challenging. | The rights of the unborn child are violated, as they cannot provide consent. |
| Enhances quality of life. | Risk of causing unintended harm. | Getting healthy alleles into the nucleus is challenging. | It causes irreversible changes, the long-term outcomes of which are not fully understood. |
| Germline gene therapy allows carrier parents to have children free from genetic disorders. | Diverts scarce healthcare resources. | Maintaining the expression of healthy alleles is challenging. | It could be used for non-therapeutic enhancements, such as selecting desirable traits. |
| Reduces the overall disease burden in the population. | It is high cost, which may restrict access. | Effects are short-term as somatic cells have a limited lifespan and are replaced by cells with the faulty allele. |
To ensure gene therapy is applied ethically and safely, regulation is essential. Achieving an appropriate ethical balance is a critical, ongoing challenge.