Question

Name the three diseases against which gene therapy has proved successful.

Answer 1

Hint it is an experimental technique that uses genes to treat or prevent disease. In future this technique is used to treat a disorder by inserting a gene into a patient's cells instead of using drugs or surgery.

Complete answer: To answer this Question you must know what gene therapy is.
Replacement of non-functional genes with functional genes is called gene therapy.
1. Sickle cell disease (SCD) is an inherited blood disorder that leads to the production of abnormal haemoglobin. Sickle cells work by knocking down the expression of the BCL11A gene in case of gene therapy to flip the switch back fetal haemoglobin, which does not sickle, and directly reduce sickling haemoglobin.
2. Haemophilia is a genetic bleeding disorder caused by a mutation in the F8 gene that leads to low levels of a protein called factor VIII and factor VII is necessary for blood clotting. In gene therapy a normal F8 factor is modified into adeno-associated virus that targets liver cells. This virus acts as a vector, and is introduced into the patient's body with a single intravenous infusion. Then factor F8 enters into the liver cells, enabling the body to make factor VII.
3. Cancer :- There are multiple gene therapies that have been developed to treat a wide variety of cancers ,including brain cancer ,breast cancer, liver, skin, colon cancer ect. in which the cancerous part is eliminated by inserting the healthy and functional cells.

Note: to perform gene therapy , a patient's blood stem cells are collected and exposed to a vector containing instructions to knock down BCL11A. The magnitude ,timing and durability of the response to haemophilia gene therapy is broad. There are lots of diseases which can be treated with the help of gene therapy such as neurodegenerative disease , blindness etc.