# Hox genes location on chromosomes **URL:** \ **Category:** Factual Questions\ **Created:** [November 11, 2007, 10:27pm UTC](https://boards.straightdope.com/t/hox-genes-location-on-chromosomes/426052 "2007-11-11T22:27:09Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![misterW](https://avatars.discourse-cdn.com/v4/letter/m/f1d935/32.png) [@misterW](https://boards.straightdope.com/u/misterW)\ **Post date:** [November 11, 2007, 10:27pm UTC](https://boards.straightdope.com/t/hox-genes-location-on-chromosomes/426052/1 "2007-11-11T22:27:09Z")
I was recently reading a piece about hox genes (the genes whose expression lets cells know what segment of an organism they are in and thus what type of cells to develop into) and it said that hox genes are _arranged in the same order on a chromosome as the body segments they influence – basically in some kind of head to tail order_. This seems that this would be an incredible coincidence for chance alone to account for it-- there must be some reason for it. But why is it? Why would the location of genes on a chromosome in any way resemble the layout of the physical body of an organism? I mean, if I was designing an organism from scratch, I might lay genes out on a chromosome in such a way, just so I wouldnt get confused, but thats obviously not what we’re talking about here. Ideas? ---
**Author:** ![Harmonix](https://avatars.discourse-cdn.com/v4/letter/h/3ec8ea/32.png) [@Harmonix](https://boards.straightdope.com/u/Harmonix)\ **Post date:** [November 11, 2007, 11:46pm UTC](https://boards.straightdope.com/t/hox-genes-location-on-chromosomes/426052/2 "2007-11-11T23:46:16Z")
Can you link to that article? my **WAG** (bold WAG) would be that these hox genes code for a receptor of some sort and that they are ver y similar to each other. Similar genes like this are called gene families and they develop by duplication and differential mutation of the genes. This would explain the physical proximity, but not nessecarily the order. Perhaps you misread it and it said they were activated in some sort of well defined sequential order? as opposed to a physical order. In anycase it doesn’t argue for an intelligent designer unless you WANT it to argue for design. ---
**Author:** ![misterW](https://avatars.discourse-cdn.com/v4/letter/m/f1d935/32.png) [@misterW](https://boards.straightdope.com/u/misterW)\ **Post date:** [November 12, 2007, 1:32am UTC](https://boards.straightdope.com/t/hox-genes-location-on-chromosomes/426052/3 "2007-11-12T01:32:11Z")
[QUOTE=Harmonix] Can you link to that article? my **WAG** (bold WAG) would be that these hox genes code for a receptor of some sort and that they are ver y similar to each other. Similar genes like this are called gene families and they develop by duplication and differential mutation of the genes. This would explain the physical proximity, but not nessecarily the order. Perhaps you misread it and it said they were activated in some sort of well defined sequential order? as opposed to a physical order. In anycase it doesn’t argue for an intelligent designer unless you WANT it to argue for design. [/QUOTE] Sorry, I dont have a link. This was from The Ancestor’s Tale by Richard Dawkins. The chapter is The Fruit Fly’s Tale. Here, I’ll type out a short excerpt for u: _“…It would be even tidier if the Hox genes were arrayed along the length of a chromosome, in the same order as the segments they influence. Well, it isnt quite as tidy as that, but it very nearly is. The Hox genes are indeed arranged in the right order along one chromosome…”_ But this information on the layout of hox genes can be found in biology textbooks as well. It was just rereading it in Dawkin’s book that got me thinking about it again. To respond to your other comments: I agree – I’m not surprised that they are grouped together due to their origin from duplication. But this doesnt explain why they are grouped in that particular order. Hox genes code for transcription factors, which enable them to turn on other genes that code for the development of anatomical features peculiar to each body segments. I’m not trying to argue for an intelligent designer (lol); I’m just trying to find an explanation for this. ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [November 12, 2007, 5:51pm UTC](https://boards.straightdope.com/t/hox-genes-location-on-chromosomes/426052/4 "2007-11-12T17:51:27Z")
I believe the order is still a mystery. At least, according to the evolutionary biology prof I had a few years ago. Hopefully somebody will come along with a better cite. ---
**Author:** ![Anaglyph](https://avatars.discourse-cdn.com/v4/letter/a/ed8c4c/32.png) [@Anaglyph](https://boards.straightdope.com/u/Anaglyph)\ **Post date:** [November 13, 2007, 7:47am UTC](https://boards.straightdope.com/t/hox-genes-location-on-chromosomes/426052/5 "2007-11-13T07:47:48Z")
Here’s a recent review article that shows that within Drosophila, the arrangement of the Hox gene cluster is fairly dynamic > [@](#): > > HOM-C evolution in Drosophila: is there a need for Hox gene clustering? > Bárbara Negre and Alfredo Ruiz > Trends in Genetics , Volume 23, Issue 2, February 2007, Pages 55-59 > > The conservation of Homeotic (Hox) gene clustering and colinearity in many metazoans indicates that functional constraints operate on this genome organization. However, several studies have questioned its relevance in Drosophila. Here, we analyse the genomic organization of Hox and Hox-derived genes in 13 fruitfly species and the mosquito Anopheles gambiae. We found that at least seven different Homeotic complex (HOM-C) arrangements exist among Drosophila species, produced by three major splits, five microinversions and six gene transpositions. This dynamism contrasts with the stable organization of the complex in many other taxa. Although there is no evidence of an absolute requirement for Hox gene clustering in Drosophila, we found that strong functional constraints act on the individual genes.