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Topic: Hox genes

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	Homeobox
		Genes that have a homeobox are called Hox genes and form the Hox gene family.
		Hox genes determine where limbs and other body segments will grow in a developing fetus or larva.
		The Hox genes were first found in the fruit fly Drosophila melanogaster and have subsequently been identified in many other species, from insects to reptiles and mammals.
	www.ebroadcast.com.au /lookup/encyclopedia/ho/Hox_gene.html (271 words)

	Homeobox - Encyclopedia, History, Geography and Biography (Site not responding. Last check: 2007-09-10)
		A homeobox (or homoeobox) is a DNA sequence found within genes that are involved in the regulation of development (morphogenesis) of animals, fungi and plants.
		Genes that have a homeobox are called homeobox genes and form the homeobox gene family.
		Plants and animals do not share the same homeotic genes, and this suggests that homeotic genes were evolved once in the early evolution of animals and once again in the early evolution of plants.
	www.arikah.com /encyclopedia/Hox (526 words)

	Limbs, hox genes, and evolution
		The most 3' gene, hoxD-9, is expressed over the entire limb bud, while more 5' genes' expression is increasingly restricted to the posterior of the limb, so that hoxD-13 has the smallest expression domain, restricted to the extreme posterior of the limb bud where it is coexpressed with the four other hox genes (Figure 1b).
		The genes are expressed in a pattern reminiscent of hox gene expression in the trunk, in which expression of more 5' genes is nested inside the expression domains of more 3' genes.
		While the pattern of hox gene expression schematized in Figure 1 is useful in characterizing the peculiarities of autopod development, the in vivo expression appears somewhat different.
	www.sccs.swarthmore.edu /users/99/mahowald/limb-evol.html (2436 words)

	Homeobox genes - EvoWiki (Site not responding. Last check: 2007-09-10)
		HOX genes are a particular group of homeobox genes which are found in hox clusters.
		HOX genes are famously found in clusters, possibly because mixing of HOX genes by crossing over would cause fatal development problems.
		Structural complexity is not thought of as mutations or "evolution" of the hox gene, rather, the number of hox genes dictates the structural complexity of the organism.
	wiki.cotch.net /index.php/Homeobox_genes (553 words)

	firebrat Hox genes
		These genes are famous for the bizarre phenotypes that result when they are mutated -- flies grow legs out of where the antennae are supposed to be, or have legs instead of mouthparts, or they have two pairs of wings instead of one.
		Because Hox genes are so important for assigning identity along the anterior-posterior axis of the embryo, they seemed to be likely candidates for genes that can reshape the body plan during evolution (see my work on centipedes for more on this concept).
		Expression patterns of the rogue Hox genes Hox3/zen and fushi tarazu in the apterygote insect Thermobia domestica.
	www.salk.edu /labs/mnl-t/clh/geneevol.html (915 words)

	Hox genes in vertebrates
		In general, homeotic phenotypes observed in specific hox gene mutations are restricted to the anterior boundary of expression.
		The earliest expression studies focused on the expression of hox genes in the prevertebra of mid-gestation embryos.
		Although various hox gene have been found to be expressed in soft tissues such as the lung, gut, etc., little is known about whether this expression is the result of segmentation (i.e., being derived from trunk neural crest migration) or whether this expression is de novo.
	www.ucalgary.ca /UofC/eduweb/virtualembryo/hox.html (2741 words)

	[No title]
		The Hox gene family is present in animals across phyla and has the potential to explain major changes of the bauplan (body plan - the overall layout of the body).
		Another study, Regulation of number and size of digits by posterior Hox genes: a dose-dependent mechanism with potential evolutionary implications showed that as the amount of HOX gene product present in mouse embryos was gradually reduced, embryo effects led first to ectrodactyly, then to olygodactyly and then to adactyly (no fingers).
		Also, please note that the Hox genes are known to occur in clusters - gene families, groups of closely related (but not identical genes) that are produced by gene duplications - which have been observed in the laboratory.
	www.gate.net /~rwms/EvoLimb.html (689 words)

	HOX Genes (Site not responding. Last check: 2007-09-10)
		Hox genes coordinate the formation of the branchial region of vertebrate embryos, which involves neural crest cells, visceral arches, and the developing brain.
		There are a number of Hox genes, which are selectively expressed in cells based on their initial location in the fetus.
		Neural crest cells migrating from the hindbrain express a combination of Hox genes depending upon their initial locus in the brain.
	www.brown.edu /Courses/BI0032/neurcrst/hox.htm (156 words)

	The Molecular History of Eukaryotic Life
		There, evidence is cited for one hox cluster in acorn worms (a hemichordate), two hox clusters in amphioxus (a cephalochordate) and three (or 4) in lamprey (a primitive vertebrate).
		The ParaHox gene cluster is an evolutionary sister of the Hox gene cluster.
		Homeobox genes in the ribbonworm Lineus sanguineus: evolutionary implications.
	drnelson.utmem.edu /MHEL.hox.html (1343 words)

	Retinoic Acid and Hox Gene Regulation (Site not responding. Last check: 2007-09-10)
		RA was initially associated with the regulation of Hox genes from studies examining the differentiation of teratocarcinoma cells.
		Low levels of RA were found to induce the transcription of genes near the 3' end of the cluster, while genes farther away from the 3' end of the cluster required a longer time period and higher concentration of retinoic acid was required to activate the transcription of the Hox gene (Langston and Gudas, 1994).
		Although each gene in the cluster is being transcribed in the 5' to 3' direction, activation by retinoic acid occurs in the 3' to 5' direction in mammalian development.
	www.sccs.swarthmore.edu /users/98/wu/hox.html (1514 words)

	Hoax (sp?) Genes - NewCreationism.Org Article #17
		Hox genes determine which genes are expressed ("turned on") and which are not ("turned off") during genetic development.
		And ultimately, this is why we shouldn't be surprised that the Homebox genes which control eye development in insects which have multilensed eyes also control the development of the very morphologically different single lensed eyes found in vertebrates.
		Indeed, Hox genes represent a level of biological abstraction that the theory of random evolution does not predict.
	www.newcreationism.org /CreationArticle17.html (909 words)

	The Scientist : Surprise, Surprise: Hox Proteins Have Evolved (Site not responding. Last check: 2007-09-10)
		Hox genes are clusters of regulatory genes that control development by turning other genes on and off.
		Biologists considered the Hox genes so conserved and their sequences so similar that their encoded proteins were practically interchangeable between species as disparate as flies and mice.
		The Distal-less gene (in green) is expressed in the appendages' distal regions, Cubitus interruptus (in red) and engrailed (in blue) are expressed in the embryo's anterior and posterior compartments.
	www.the-scientist.com /article/display/13315 (1562 words)

	The Panda's Thumb: Jellyfish lack true Hox genes!
		What that means is that you find the Hox genes that are essential for specifying positional information along the length of the body in a group on a chromosome, and they are organized in order on the chromosome in the same order that they are turned on from front to back along the body axis.
		Hox genes are not the only genes that are important in this process, of course; animals also use another class of regulatory genes, the Wnt genes, to regulate development, for instance.
		Genes containing a homeobox are older still, and are found in plants and animals, but the particular genes of the Hox system are unique to multicellular animals, and that key organization arrangement of the set of Hox genes in a cluster is more unique still.
	www.pandasthumb.org /archives/2006/05/jellyfish_lack.html (1104 words)

	Pharyngula: A brief overview of Hox genes
		Many people have at least heard of the particular set of genes, the Hox genes, that are responsible for assigning specific regional identities on body parts (Ed Lewis won the Nobel for his work on them, for one thing).
		Hox genes are a subset of homeotic genes that contain a homeobox, and are also found in a homeotic complex.
		The little circles represent subdomains of Hox gene expression—one of the things the organism can also do is express sub-segmental patches of a different Hox gene, bringing in the whole subsequent module of gene recruitment to that area and adding a bit of abdominal character, for instance, to a particular feature of that segment.
	scienceblogs.com /pharyngula/2006/04/a_brief_overview_of_hox_genes.php (2227 words)

	Pharyngula::Hox genesis
		The Hox genes are part of a class of transcription factors that use a homeodomain to bind DNA, but there are also other homeodomain-containing transcription factors that are not within a Hox cluster.
		The individual genes are also present, but not clustered, in invertebrates—the idea is that whatever factor keeps the genes clustered is present in chordates, but was lost in invertebrates, so that their ParaHox genes have been gradually scattered about within their genome.
		The expression of the Hox genes is mainly associated with ectodermal derivatives—in particular, the neurectoderm.
	pharyngula.org /index/weblog/comments/hox_genesis (3511 words)

	Hox Genes in Platyhelminthes (Site not responding. Last check: 2007-09-10)
		The Hox gene expression leads to the formation of key components in the adult body plan such as limbs or heads.
		The goal of scientists today is to characterize Hox genes in various phyla to help support the universal function these genes seem to play in animal axis determination.
		KSP 3 aligned 100% with the flour beetle strain GA-1 HOMC gene cluster, 96% alignment with the acorn worm Hox 11/13a mRNA, and 100% alignment with the homeobox protein (Hox A1) found in the frog.
	www.winthrop.edu /biology/Smnrs/04sabstracts/smith.htm (316 words)

	The clustering of Hox genes is not necessary for their proper function
		The Hox genes (also known as homeotic genes) play a crucial role in the development of animals, being involved in the determination of segment identity along the body axis.
		The Hox genes are arranged in the fly genome in a striking manner: they are clustered and their order is the same as that of the body segments they act upon.
		This organization is conserved in the genome of most animals where the Hox genes are arranged in a similar way as in the fly genome.
	www.eurekalert.org /pub_releases/2005-05/uadb-tco050205.php (450 words)

	Cnidarians Reveal Intermediate Stages in the Evolution of Hox Clusters and Axial Complexity -- Finnerty 41 (3): 608 -- ...
		Symbols for Hox genes and ParaHox genes are the same as in Figure 3.
		The central Hox class may have originated in the common ancestor of bilaterians and grew to include four or five genes prior to the divergence of protostomes from deuterostomes.
		Homology of hox genes and the zootype concept in early metazoan evolution.
	icb.oxfordjournals.org /cgi/content/full/41/3/608 (4162 words)

	EVOLUTIONARY BIOLOGY: ON THE CLUSTERING OF HOX GENES
		They have shown that the vertebrate Hox genes demonstrate not just spatial but also temporal collinearity; that is, genes at one end of the complex are expressed not only in the anterior of the embryo, but also relatively early in development.
		Drastic alterations, such as the outgrowth of a limb instead of an antenna or of a wing in place of a haltere, are associated with the misexpression of gene members of the Hox family of transcription factors.
		Twenty-five years ago, Lewis showed that Hox genes were clustered along the chromosome, colinear with their domains of action in the thorax and abdomen of flies.
	scienceweek.com /2004/sb041008-1.htm (1389 words)

	Establishing neuronal circuitry: Hox genes make the connection -- Briscoe and Wilkinson 18 (14): 1643 -- Genes and ...
		Hox genes and the ectopic expression of Hox genes in chick embryos
		genes by migrating neural crest cells is not indicative of an
		Murphy, P. and Hill, R. Expression of mouse labial-like homeobox-containing genes, Hox 2.9 and Hox 1.6, during segmentation of the hindbrain.
	www.genesdev.org /cgi/content/full/18/14/1643 (3811 words)

	facegene: University of Utah News Release: October 7, 2003
		The genes are common to all mammals, and so they likely help control human facial expressions such as smiles and frowns.
		It is called gene targeting, and involves disabling or “knocking out” various genes in mice to see what goes wrong, thus learning what the genes normally do.
		The study deals with what are called homeobox or Hox genes, which are genes that orchestrate the actions of other genes to guide embryo development.
	www.utah.edu /unews/releases/03/oct/facegene.html (1354 words)

	The homeobox page (Site not responding. Last check: 2007-09-10)
		The first genes found to encode homeodomain proteins were Drosophila developmental control genes, in particular homeotic genes, from which the name "homeo"box was derived.
		HOX cluster: The term Hox cluster refers to a group of clustered homeobox genes, named Hox genes in vertebrates, that play important roles in pattern formation along the anterior-posterior body axis.
		A Comprehensive Classification of Homeobox Genes, Bürglin, T.R. (1994) in Guidebook to the Homeobox Genes.
	homeobox.biosci.ki.se (1847 words)

	Suprising new information on the HOX genes
		From insects to human beings HOX genes are lined up tightly together in the chromosomes like pearls on a string.
		In other words, the HOX gene sitting first in line on the chromosome controls for example the development of the back part of the brain, the second gene is responsible for the upper part of the neck and so on along the body axis.
		These genes are not lined up tightly at all, but it still seems that their function is about the same as in animals where the genes are closer together.
	www.news-medical.net /?id=4693 (533 words)

	History: On Hox Genes (Site not responding. Last check: 2007-09-10)
		In the 1980s, researchers discovered a series of genes called Hox genes that set the identity of segments of insect bodies from head to tail.
		Mutations to Hox genes can put an entire leg where an antenna should sprout out (right) and produce other equally grotesque transformations.
		(Our version of the gene can be inserted in a fly and still trigger the building of an insect eye!) It now appears that some 600 million years ago, a common ancestor of most animals on Earth today acquired a “genetic toolkit” of these body-building genes.
	evolution.berkeley.edu /evosite/history/hox.shtml (168 words)

	University of California, San Diego: External Relations: News & Information: News Releases : Science
		genes in fruit flies that control the placement of the head, thorax and abdomen during development are a generalized feature of all animals, including humans.
		The UCSD team’s demonstration of how a mutation in the Ubx gene and changes in the corresponding Ubx protein can lead to such a major change in body design undercuts a primary argument creationists have used against the theory of evolution in debates and biology textbooks.
		In addition, the discovery in the UCSD study, which was financed by the National Institute of Child Health and Human Development, of how this particular Hox gene regulates limb development also may have an application in improving the understanding human disease and genetic deformities.
	ucsdnews.ucsd.edu /newsrel/science/mchox.htm (947 words)

	IngentaConnect Evolutionary Plasticity of Vertebrate Hox Genes (Site not responding. Last check: 2007-09-10)
		A dramatic demonstration of this conservation is seen in the expression and function of Hox genes deployed along the animal anterior-posterior (A-P) body axis, where similar expression and function of Hox genes are seen in animals as diverse as nematodes, insects and vertebrates.
		General patterns of Hox cluster evolution among the major lineages of vertebrates are described including lineage-specific instances of cluster duplication and gene loss.
		Following this are brief descriptions of the evolving role of Hox genes in evolution of primitive vertebrates, and their subsequent roles in evolution of vertebrate axial and appendicular diversity.
	www.ingentaconnect.com /content/ben/cg/2004/00000005/00000006/art00001 (273 words)

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