Which of the following statements regarding gene therapy is/are correct ?

Options

A. it is an application of biotechnology, in which a defective gene is manipulated by a introduction of a normal, healthy and functional gene
B. the genetic disorders that are being investigated for gene therapy, range from sickle- cell anaemia to serve combined immuno-deficiency (SCID))
C. the first clinical gene therapy was given in 1990 to a 4 year old girl with adenosine deaminase (ADA) deficiency
D. all of these

Answer

4