This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetic Disorders, Subject name: Biochemistry
In 1990, for the first time, Michaele Blease and W. French Andresco of National Institute of Health, Bethesda, U.S.A. attempted gene therapy on a human patient. Which of the following disease was attempted to be cured? 
Select and explain. 
A. Cystic fibrosis, B. Haemophilia, C. Thalassemia, D. Severe Combined Immunodeficiency Disease
D: Severe Combined Immunodeficiency Disease
Answer: D: Severe Combined Immunodeficiency Disease 
Explanation: The first convincing therapeutic effect from gene transfer occurred with : SCID Impoant types of defects in SCID: X-linked Severe Combined Immunodeficiency Disease (SCID): mutations in the gene (IL2RG). IL2RG encodes gc subunit of cytokine receptors. Inheritance pattern: X-Linked. Most common defect in SCID patientsQ. Most common cause of SCID is IL2R defect. Autosomal Recessive SCID: ADA (Adenosine Deaminase enzyme) deficiency. gene therapy is done for ADA deficiency SCID.