For this lesson, students are guided through the steps necessary to compare nucleotide and amino acid sequences available at the National Center for Biotechnology Information that is maintained by the National Institutes of Health. The lesson starts with an examination of the alpha-globin gene. Alpha-globin is one of the proteins that constitutes hemoglobin. Student look at the various sequences of this gene that have been deposited at NCBI with a goal of determining alternative forms of the gene. The lesson then broadens the scope of comparison to include members of the globin protein family. Students create a phylogenetic tree that illuminates the similarities between some of the members of this protein family to explore how the human genome has developed over time. The results of a third sequence comparison highlight the use of the globin protein as a marker to create a phylogenetic tree of different species of animals, plants, bacteria, and viruses.