SCIENTIFIC THINKING There are difficulties inherent in testing hypotheses involving human health. Imagine that you have ­developed a potential vaccine against AIDS. Given the nature of the disease, all testing must be conducted in humans. Can you ­design an ethical but effective experiment?

A biologist isolated a gene from a human cell, inserted it into a plasmid, and inserted the plasmid into a bacterium. The bacterium made a new protein, but it was nothing like the protein normally produced in a human cell. Why? (Explain your answer.)a. The bacterium had undergone transformation.b. The gene did not have sticky ends.c. The human gene contained introns.d. The gene was not synthesized from scratch.

Potato blight causes potato plants to shrivel and rot. The disease is caused by the pathogen Phytophthora infestans, infamous for its role in Ireland's Great Potato Famine in the mid-1840s. The disease can devastate crops during wet weather, sometimes leading to total crop loss. Researchers aim to use recombinant DNA methods to transfer blight resistance genes from resistant varieties into susceptible varieties of potato.Explain how restriction endonucleases and DNA ligase could be used to insert a potato blight resistance gene into a plasmid.

Explain how you might engineer E. coli to produce human growth hormone (HGH) using the following: E. coli containing a plasmid, DNA carrying the gene for HGH, DNA ligase, a restriction enzyme, equipment for manipulating and growing bacteria, a method for extracting and purifying the hormone, and an appropriate DNA probe. (Assume that the human HGH gene lacks introns.)

Potato blight causes potato plants to shrivel and rot. The disease is caused by the pathogen Phytophthora infestans, infamous for its role in Ireland's Great Potato Famine in the mid-1840s. The disease can devastate crops during wet weather, sometimes leading to total crop loss. Researchers aim to use recombinant DNA methods to transfer blight resistance genes from resistant varieties into susceptible varieties of potato.Explain how restriction endonucleases and DNA ligase could be used to insert a potato blight resistance gene into a plasmid.