Every organism has a unique body plan.
During growth of the embryo, arms and legs develop differently due to the action of special genes. Certain genes that determine how parts of the body are shaped, or patterned, are called homeotic genes . Similar patterning genes are found in a wide variety of organisms. Homeotic gene organization is conserved through evolution Mutations in mammalian homeotic genes Homeotic mutations could be involved in evolutionary change. This activity was developed through the Natural History of Genes, a University of Utah program funded by the Howard Hughes Medical Institute.