What was the source of insulin before it was produced using rDNA techniques?

Step-by-step solution

Management of adult-onset diabetes is possible by taking insulin at regular time intervals. What would a diabetic patient do if enough human- insulin was not available? If you discuss this, you would soon realise that one would have to isolate and use insulin from other animals. Would the insulin isolated from other animals be just as effective as that secreted by the human body itself and would it not elicit an immune response in the human body? Now, imagine if bacterium were available that could make human insuli