Sometimes, replication mistakes or an organism's environment causes changes in its genetic code. Since homeotic mutant phenotypes can lead to differences in body shapes and structures, homeotic mutations should be an effective means for evolution change. If a change in body shape or structure leads to an advantage for an organism, perhaps allowing it to capture food more effectively or allowing it escape from it's predators faster, and then it is a beneficial mutation. Although some mutations help the survival rate for some organisms, many mutations are virulent. They can cause deformities, which make it hard for organisms to survive in its once well-adapted environment.
Homeotic genes are special genes which control the formation of whole organisms or body parts.
Homeotic genes determine the identity of body segments in the anterior-posterior axis in Drosophila flies. If mutations occur in homeotic genes a dramatic change is caused. Body parts such as legs can develop in places other than where they are suppose to. The first homeotic mutant was discovered in 1915, in a Drosophila fly. This mutant was described as having a second pair of wings where the balancing organ belonged.