What is a Homeobox?

Mary McMahon
Mary McMahon

A homeobox is a sequence of DNA coded to express a protein that will bind to other DNA and regulate the way it expresses. Homeoboxes were discovered in the 1980s by genetic researchers, initially in fruit flies — a heavily studied organism in genetics — and later in other organisms as well, including simple and single-celled organisms. These sequences play a very important role in embryonic development, determining how and where genes express, and are among a group of genetic sequences involved in regulation and expression of genes as organisms develop.

Homeoboxes were first discovered in fruit flies.
Homeoboxes were first discovered in fruit flies.

There are typically around 180 base pairs in a homeobox. The protein it codes for has around 60 amino acids and is capable of binding to DNA to turn it on or off, determining whether it expresses. In the course of embryonic development, the homeobox tells cells when and where to start producing, mapping out the basics of the organism and laying the groundwork for more advanced development as cells differentiate under the direction of proteins produced by the homeoboxes and other gene sequences.

A number of human homeobox genes have been discovered across several chromosomes.
A number of human homeobox genes have been discovered across several chromosomes.

Initially, researchers suspected the regulatory processes behind embryonic development were very different in organisms of different species, especially organisms only distantly related. The discovery of these gene sequences showed that organisms from slugs to elephants relied on homeoboxes for regulation of their DNA during development. Errors in these sequences can also result in developmental abnormalities, as the development of the organism gets confused and traits express in the wrong places.

A number of human homeobox genes have been discovered, across several chromosomes. These sequences have been studied to learn more about the proteins they code for and how those proteins work. Research on organisms like fruit flies can be directly applied to human genetics, as in many cases the genes act in similar ways. Understanding how alterations in a fruit fly homeobox affect development can provide information about how similar alterations might change the way a human embryo develops.

A wide variety of processes are involved in embryonic development. These genes are not the only determining factor, and embryos can also be influenced by outside factors such as exposure to toxins, which can lead to deformities caused by disruptions in DNA expression. Understanding the myriad complexities involved in development helps researchers understand what happens when development goes wrong, and why. This can be applied to research designed to address errors in development with the goal of preventing them in the future.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


Homeobox genes are specifically involved in the placement and type of structures in embryos. They are selector genes that determine where a structure is built but which structure actually does get built depends on different sets of genes for each particular species.

As the article suggests, the whole subject of gene expression is quite complex. Fascinating, but very complicated!


I'm trying to see how exactly this fits in with transcription, introns and exons - part of the mRNA synthesis? Or is it part of how the mRNA molecule alters the DNA "message"? It sounds like the homeobox is specific to embryo development but does it continue after the organism is initially formed?

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