Homeotic gene
Homeotic genes are genes which regulate the development of anatomical structures in various organisms such as echinoderms,
Mutations in homeotic genes cause displaced body parts (homeosis), such as antennae growing at the posterior of the fly instead of at the head.[3] Mutations that lead to development of ectopic structures are usually lethal.[4]
Types
There are several subsets of homeotic genes. They include many of the
They also include the MADS-box-containing genes involved in the ABC model of flower development.[8] Besides flower-producing plants, the MADS-box motif is also present in other organisms such as insects, yeasts, and mammals. They have various functions depending on the organism including flower development, proto-oncogene transcription, and gene regulation in specific cells (such as muscle cells).[9]
Despite the terms being commonly interchanged, not all homeotic genes are Hox genes; the MADS-box genes are homeotic but not Hox genes. Thus, the Hox genes are a subset of homeotic genes.
Drosophila melanogaster
One of the most commonly studied
During development (starting at the blastoderm stage of the embryo), these genes are constantly expressed to assign structures and roles to the different segments of the fly's body.[13] For Drosophila, these genes can be analyzed using the Flybase database.
Research
Much research has been done on homeotic genes in different organisms, ranging from basic understanding of how the molecules work to mutations to how homeotic genes affect the human body. Changing the expression levels of homeotic genes can negatively impact the organism. For example, in one study, a pathogenic phytoplasma caused homeotic genes in a flowering plant to either be significantly upregulated or downregulated. This led to severe phenotypic changes including dwarfing, defects in the pistils, hypopigmentation, and the development of leaf-like structures on most floral organs.