Molecular evolution: evolution in multigene families
Those of us who spend our lives thinking about large, multicellular organisms tend to forget that many genes occur in large families. The one most of you probably know about is the multigene family coding for ribosomal RNA. You may not know that it shows a peculiar pattern of sequence evolution, which happens to make it more useful for molecular phylogenetics than it would otherwise be. You may or may not know that other multigene families include globin genes (myoglobin, alpha-globin, and beta-globin) and many others. Globin genes follow a different pattern of evolution and introduce the problem of distinguishing orthology from paralogy.