What is hox genes?

Question

I need information about "Hox Genes",and speicially in fishes.
Tell me what is that? what do? where on the body can be found? and please give me some refs and sites about it.

Answer 1

Genes are not found "on" the body.

Here is the wikipedia article:
http://en.wikipedia.org/wiki/Hox

Answer 2

These genes became known as 'Homeobox', or 'Hox' genes (derived from the term 'homeosis' , meaning the developmental transformation of a body segment). It was subsequently discovered that mammals possess four sets, or 'clusters', of Hox genes as opposed to the single set controlling development in the fruit fly. By studying these gene clusters in other species, it has become clear that their overriding mechanism, as well as their basic genetic codes, have been highly conserved across evolution and time, suggesting an early development in the history of life.

Hox genes act by producing proteins in the developing embryo. These proteins act at the tip of a developmental cascade, turning on their target genes by directly binding to very specific DNA sequences preceding the other gene codes, thus causing these target genes to produce new proteins themselves (see Figure 2) . Like a set of molecular dominoes, they recruit a host of protein messengers that lay down the pattern of the basic body plan. All these developmental molecules are expressed in highly specific concentrations that percolate across regions of the embryo in a gradient which lets every cell know exactly where it is in relation to its neighbours and, more importantly, exactly what type of cell it is to become if it is to effectively participate in the overall scheme of things. But, one must again ask a question: if all animals utilise this common conserved mechanism with the same or similar genes for development, why don't all animals look exactly alike?

The key determining factors are (1) concentration ; (2) location ; (3) timing ; and (4) target gene specificity . Since common species possess these highly similar developmental genes, differences of body shape are generated by evolutionary changes in the concentration or amounts of the Hox proteins produced; the location of their production in the developing embryo; and the timing with which they become active in the body plan. The fourth factor, target gene specificity, crucially affects the former three, for if a given Hox gene sequence is altered by mutation, the resulting Hox protein that is expressed may not bind to its target genes and therefore will not attain the required concentration in a given location or time. Alternately, it may bind to a different target gene than it does in other members of the species. Any such changes result in alterations in the body form. It is rather like cutting a new groove into the surface of an old key, that, whilst it may not open the same door, it may fit perfectly into an entirely different lock. Such subtle changes in any of these factors may result in acute, catastrophic mutations, such as antennapedia , or slight, subtle alterations with no overt consequences for the animal as a whole.


Figure 2. Homeobox protein bound to DNA.

Hox gene research has opened up exciting new prospects not only for a novel perspective on evolution at the molecular level but also for potential medical advances. As understanding precedes advancement, it is hoped to gain a thorough knowledge of how this system functions as a whole in order to generate new strategies for treating some forms of leukaemia and developmental abnormalities. The discovery of these genes has opened a new and beautifully complex window into the development of new life - in the process, revealing an undeniable molecular kinship between all species. In the words of the philosopher Paul Weiss, 'But nature is not atomised. Its patterning is inherent and primary, and order underlying beauty is demonstrably there; what is more, the human mind can perceive it only because it is itself part and parcel of that order'.

Answer 3

try this sites

http://www.ucalgary.ca/UofC/eduweb/virtualembryo/hox.html

http://www.irishscientist.ie/2000/contents.asp?contentxml=156s.xml&contentxsl=insight3.xsl