homeotic

Homeotic is an adjective used in biology to describe processes, genes, or mutations that relate to homeosis—the transformation of one organ or body part into another during development. In genetics and developmental biology, homeotic elements control patterning along body axes and specify the identity of developing segments or structures.

Homeotic mutations produce structural transformations, such as a leg forming in place of an antenna in fruit flies. These phenotypes revealed that particular genes regulate positional information rather than just growth, establishing a genetic basis for body plan formation across diverse animals.

Most well-characterized homeotic genes encode transcription factors containing a homeobox, a conserved DNA-binding domain. In animals, these genes are organized into Hox (and related) clusters that exhibit colinear expression along the anterior-posterior axis. In plants, analogous genes such as MADS-box family govern organ identity in flowers. The discovery of these genes showed that the same genetic framework can pattern very different organisms.

Historically, work on Drosophila and other model organisms in the late 20th century led to a widely accepted view that evolutionary changes in body plans reflect changes in homeotic gene regulation. The term homeotic derives from homeosis, the concept of organ identity being altered by genetic control.

See also: Homeobox; Hox gene; Homeotic gene; Evolutionary developmental biology.