“Describe and explain two processes that account for the differences in the number of his genes present in humans, when compared to those present in the worm C Elegans.”
One process could be hox gene inversions causing duplications, and the other translocation ?? I don’t really understand either of these... any help would be greatly appreciated!
I know that the HOX genes are a subregion within the homeobox, but I'm unsure how those relate to homeotic genes. All I'm fully sure of is that they all contribute to the spatial organization of organs and body parts during embryonic development.
TLDR: Why are Hox genes physically ordered within the (fruit fly, and presumably human) genome in the physical order in which they are expressed in the body? Does it have something to do with recombination?
I came across this curious fact in Endless Forms Most Beautiful, having earlier heard it mentioned in Your Inner Fish. Both books mentioned the miraculous fact that Hox genes, which control ultra basic developmental functions such as eye and limb formation, are found in the genome in the general order of the body. That is, developmental genes (in a fruit fly, but us too) influencing the head are in a cluster, then genes influencing the thorax, then genes influencing the abdomen. At least, this is what I think they said. Both books mentioned it as a miraculous occurrence, but neither told why it has to be that way. Why the heck should the physical order of genes in DNA matter, so long as the genes are on the proper chromosomes and are properly expressed? Might they be linked to reduce the likelihood that recombination messes things up? Even still, that wouldn't answer why the order is so precise. If all of the Hox genes are linked, then you could reduce recombination by having "head, abdomen, thorax" just as well as "head, thorax, abdomen."
Hopefully this is coherent, I don't really understand the subject well enough to phrase a proper question.
Thanks!
http://www.criticalcommons.org/Members/pthurtle/clips/x-files-season-5-episode-5-the-post-modern-1/view
Asked on /r/askscience but thought I might try my luck here.
I am having difficulty differentiating the three. Are Hox Genes and Gene Switches both Regulatory Genes or are they something different? My sources don't specify clearly enough.
From what I understand, homeobox genes are a large family of genes involved in directing the body structure formation.
Homeotic genes controls the identity of body parts and the proteins it codes for are transcription factors. Mutations of the homeotic genes cause structures to form in the wrong place.
Hox genes are responsible for directing the body plan along the AP axis and the proteins it codes for are transcription factors. They're a subset of the homeobox family.
Is my understanding correct? If so, what's the distinction between homeotic genes and hox genes? Are hox genes are subset of homeotic genes in that they direct the body plan along the AP axis while homeotic genes are responsible for all axes? Any help on clearing this up would be greatly appreciated!
I know these probably started out as one gene, as the Hox cluster found in eukaryotes is mostly copies of one ancestral gene. My question is concerning how the single celled organisms evolved into multicellular ones, and specialized enough to allow the Hox clusters to help directional development. Did cingle celled organisms initially form colonies in which different cells specialized in function? When does an organism go from being colonial (like a slime mold or even the man o war) to multicellular?
So recently a paper by Zelzer. E et al. in Developmental cell have shown a possible link between the Hox cluster and the development of the spinocerebellar neurons which contribute to the proprioceptive system. Does anyone know any further information of how the Hox genes contribute to the neural system?
