Final answer:
Inserting a gene from the hepatitis B virus into yeast is an example of C) genetic engineering, which is used to manufacture vaccines by producing antigenic proteins without the live virus, thereby stimulating the immune system safely.
Step-by-step explanation:
Inserting a gene from the hepatitis B virus into yeast so that the yeast produces a viral protein is an example of genetic engineering. This biotechnology technique involves manipulating an organism's genes, often to produce proteins for vaccines like the hepatitis B vaccine. The hepatitis B antigen is a viral protein which, when produced by the yeast, can be used to immunize individuals against the virus.
Moreover, genetic engineering plays a crucial role in various medical applications, including gene therapy, where a healthy gene is introduced to replace a defective one in patients. In the production of vaccines, genetic engineering ensures the vaccine contains only antigenic molecules without the pathogen's genome, significantly reducing the risk of vaccine-related illnesses.