Why won't this experiment work? For a science fair project, two students decided to repeat theÂ Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates.
A. There is no radioactive isotope of nitrogen. B. Radioactive nitrogen has a half-life of 100,000 years, and the material would be too dangerous for too long. C. Meselson and Stahl already did this experiment. D. Although there are more nitrogens in a nucleotide, labeled phosphates actually have 16 extra neutrons; therefore, they are more radioactive. E. Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.
The answer to this question is letter E. It should be noted that amino acids are also equipped with nitrogen atoms which means that it also contains proteins. The main goal of the experiment is to distinguish between the DNA and proteins but this is not possible if both of them have it.
The radioactivity will not be useful in checking what’s wrong. It is best if the two students would think of another project that may produce more productive results. It will also be advisable if they would also think of making other changes or modifications to the experiment that they want to re-do.