$ELISA$ system is based on which of the following principles?

Which of the following is used for gene transfer in animals?

In which disease is $\alpha-1$ antitrypsin used for treatment?

What is produced by genetically engineered bacteria?

The first clinical gene therapy was given in $1990$ to a $4$-year-old girl to treat deficiency of:

Correct chronological order of the steps occurring during gene therapy are
$I$. Lymphocytes are obtained from the patients
$II$. Lymphocytes are transferred to the culture dishes
$III$. Lymphocytes are transfected with the normal $ADA$ genes
$IV$. The transfected cells are returned to the patients
The chronological order should be