Evolution of Genes
The set of genes that evolve from a single ancestral gene comprise a gene family. In humans, gene families are found in many important groups of proteins, and more are being discovered as the human genome is explored. These include the globins, which carry oxygen in the blood (hemoglobin) and store it in muscle (myoglobin); the immunoglobulins (specifically, the heavy chain of the immunoglobulin), which form antibodies of the immune system; the actins, which move the cell cytoskeleton and muscle; the collagens, which form cartilage and other structural materials; and the homeotic genes, master controllers of embryonic development. There are many other examples as well.
A new member of a particular gene family is discovered by comparing its sequence to known members. This is usually done by computerized database search, and is one of the challenges of bioinformatics, a new specialty devoted to collecting and analyzing large amounts of biological information.