Humans produce insulin from certain cells in the pancreas.The insulin gene is isolated from a human pancreas cell and then inserted into a plasmid.The DNA responsible for the synthesis of insulin is then inserted into a bacterium.Figure, which is  not drawn to scale, shows how insulin can be produced in this way.  Different enzymes function at X and Y.

(a) State a general term for the technique shown in Figure

(b) Outline the roles of the enzymes that function at X and Y.

Role of enzyme at X................................................
Role of enzyme at Y................................................

(c) Explain why the plasmid is described as a vector.

(d) Outline the role of the bacterium in the process once the vector has been inserted into the host cell.