Human insulin is being commercially produced from a transgenic species of

An example of gene therapy is

Which enzyme was targeted during the first clinical gene therapy given in $1990$ to a $4$ year old girl?

Gene therapy is an attempt to correct a genetic defect by providing a normal gene into the individual. By this,the normal function can be restored. An alternate method would be to provide the gene product (protein/enzyme) known as enzyme replacement therapy,which would also restore the function. Which in your opinion is a better option? Give reason for your answer.

Which disease vaccine can be developed using recombinant $DNA$ technology?

Genetically engineered human insulin is called