Genetic Engineering

This is an imagined scenario, DNA can't be seen by humans let alone cut! 

Genetic engineering is any process by which genetic material (the building blocks of heredity) is changed in such a way as to make possible the production of new substances or new functions. As an example, biologists have now learned how to transplant the gene that produces light in a firefly into tobacco plants. The function of that gene—the production of light—has been added to the normal list of functions of the tobacco plants.

Source: http://www.scienceclarified.com/Ga-He/Genetic-Engineering.html#ixzz3n9CUopdf

Using Genetic engineering to make pure human insulin for diabetics.