Assume that you are a scientist working in the 1940's, before it was shown that DNA is the genetic material. Given that genetic information is so varied, one might think that the more diverse, variable molecule would be the genetic material.
Proteins are clearly more chemically varied.
Looking at this example of protein sequence variability compared to nucleotide sequence variability, one might think that protein is the genetic material. A particular small polypeptide is nine amino acids long. Determine the primary structure of this polypeptide. Leu N refers to the amino terminal AA in this polypeptide. Typically one writes polypeptides with the amino terminus on the left.