1. If you take a vinegar solution and add Alka Seltzer to it, you'll get a vigorous fizzing. Is whatever's in Alka Seltzer an enzyme? How might you test this?

2. Suppose you cloned the gene encoding a -amylase and put it into a potato plant in such a way that a -amylase was made in potatoes (i.e. the edible tuber). What would be the result?

3. When you eat spinach, you eat lots of enzymes that enable the spinach plant to use sunlight to convert atmospheric CO2 to sugar, i.e., to perform photosynthesis. If we eat enough spinach, could we perform photosynthesis too?

4. Reverse question. Spinach has no muscles, yet eating it can help to increase our own muscle mass. Why?

5. Maybe there's an enzyme that converts straw into gold? Suppose that such an enzyme, if it existed, would consist of 100 amino acids. Consider the following responses.

a. "Forget it. If such an enzyme were possible, someone would have found it by now."

b. "I don't know if it does exist, but I'll bet it can exist, and I'm going to find it. I'm going to synthesize in a test tube every possible 100-amino acid enzyme and test each for gold-making ability. With modern technology and a big staff, I figure I can manufacture and test about a 1000 enzymes per day. I don't care if it costs me $10,000 per day to operate, because when I find the enzyme, it's worth $50 billion easy!"

6. Predict the results of the following experiments that could have been performed in Oswald Avery's lab:

a. A Pneumococcus smooth strain (infectious) and rough mutant (harmless) are both heat-killed and coinjected into a mouse.

b. A rough mutant is ground up, and its components are coinjected with a heat-killed smooth strain.

c. A smooth strain is ground up, treated with protease (enzyme that chews up protein), and coinjected with a rough mutant.

7. You will recall that Hershey and Chase grew virus with radioactive phosphorus (to label the DNA) and radioactive sulfur (to label the protein). Then they infected E. coli with the radioactive virus and monitored how much radioactivity stayed with the cells and how much was sloughed off into the growth medium. The actual results are reproduced below. Comment on the following responses.

a. "As you can see, DNA is associated with the cells while protein is sloughed off into the medium. The experiment proves that DNA carries the genetic material that enables the virus to take over E. coli."

b. "Note that 20% of the labeled protein is associated with the cells. I say that there is a particular subset of protein that is the genetic material."

Graph not included in web version of problem set

8. You are an investigative reporter, and through a Freedom-of-Information Act request (and a big-time slipup in the bureaucracy) you've laid your hands on a top secret file describing the autopsy of nonhuman remains recovered from a metallic orb at a crash site near Roswell, New Mexico 50 years ago. The reports within give conflicting chemical analyses. Which of the claims below sound possible and which sound bogus?

a. "The alien genetic material consists of a string of glucose molecules, like beads on a string."

b. "The alien genetic material is protein-like in nature but, strangely, each molecule has two protein strands in which different amino acids pair with one another in a systematic way."

c. "The alien genetic material is surprisingly like our own. It appears to be normal DNA, except that the order of bases is fixed: adenine-cytosine-adenine-cytosine, ad infinitum."

9. Replication of DNA is very accurate: only one mistake for every billion nucleotides for every replication. Thus, the mutation of a specific gene is very rare. A gene consists of about 1000 nucleotides. Someone comes to your philanthropic foundation asking for support for the fight against the dread Purple Tongue Syndrome. He tells you that even a single mutation in the pts gene anywhere in any cell in the body is sufficient to cause the disease. He asks you for $30 million to support research on the gene. You harbor some doubts. How likely is it that a person would suffer from the disease if mutation arises only from errors in DNA replication? "Millions per year", you are told. "We don't hear about them because PTS is often misdiagnosed as lung cancer." You are not quite convinced, however, and decide to do the calculation yourself. If you find you need information not available to you, identify what you need to know, treat it as an unknown variable, and go on. But first consider if you can make a reasonable estimate of the information.