That new UCSF paper is yet another example of the intricacies of DNA and gives us a teaching moment on how science can be done in a completely different way. Consider the blood protein hemoglobin found throughout the vertebrate species, illustrated here to show its four protein chains and their many helices. Each of the four chains has about 140 amino acids which are glued together in a long line, and then fold up into a glob. Those 140 amino acids are encoded by the corresponding DNA gene. In the gene, there are three DNA nucleotides for each amino acid. For instance, the figure below shows a short segment of a human and a horse gene, both of which code for a hemoglobin chain. The letters, “ACGCT …” represent the nucleotides—small molecules that make up the DNA strand. The letters A, C, G and T stand for adenine, cysteine, guanine and thymine, respectfully. Read more