Which human medicine was the first to be produced using recombinant $DNA$ technology?

Gene therapy was first used for the treatment of ..........

Which of the following is/are correct about Adenosine Deaminase $(ADA)$ deficiency?
$I$. In the absence of adenosine deaminase enzyme,purine metabolism is disturbed and $T$-lymphocytes fail to function.
$II$. $ADA$ deficiency is caused by the deletion of the gene for $ADA$.
$III$. In some cases,it can be cured by bone marrow transplantation and enzyme replacement therapy. But in both approaches,the patients are not completely cured.
$IV$. For permanent cure,genes isolated from the bone marrow cells producing $ADA$ at early embryonic stages can be a possible cure.
Which of the above statements are correct?

Kohler and Milstein developed a method in biotechnology for the production of

In the treatment of $ADA$ deficiency during gene therapy,which cells are collected from the patient's blood?

Which of the following is based upon the principle of antigen-antibody interaction?