In mature insulin,chain $A$ and chain $B$ are interlinked by which bond?

Statement-$I$: In vitro fertilisation leading to a test tube baby is a part of biotechnology.
Statement-$II$: Developing a $\text{DNA}$ vaccine is a part of biotechnology.

Find the incorrect statement.

In which bacteria was the insulin gene cloned?

How many polypeptide chains is human insulin composed of?

The chemical structure of human insulin was studied by .........