Enzyme used in $ELISA$ test is

The two polypeptides of human insulin are linked together by

The first human drug made by using genetic engineering technique was

Statements related to human insulin are given below. Which statement$(s)$ is/are correct about genetically engineered insulin?
$(a)$ Pro-hormone insulin contains an extra stretch of $C$-peptide.
$(b)$ $A$-peptide and $B$-peptide chains of insulin were produced separately in $E. coli$,extracted,and combined by creating disulfide bonds between them.
$(c)$ Insulin used for treating diabetes was extracted from cattle and pigs.
$(d)$ Pro-hormone insulin needs to be processed for converting into a mature and functional hormone.
$(e)$ Some patients develop allergic reactions to the foreign insulin.
Choose the most appropriate answer from the options given below:

Which kind of therapy was given in $1990$ to a four-year-old girl with adenosine deaminase $(ADA)$ deficiency?

The genetic defect-adenosine deaminase $(ADA)$ deficiency may be cured permanently by