Homeobox
Homeobox (homeobox) is homologous high DNA base sequence in conjunction with the adjustment of the outbreak of an animal, a plant and fungi. The gene with homeobox is called a homeobox gene and constitutes a homeobox gene family.
There is about 180 base pair, and the homeobox encodes a protein part (homeodomain) that can bind to DNA. The homeobox gene encodes the transcription factor switching other genetic cascades typically including all genes necessary to make, for example, a foot. The homeodomain specifically binds to DNA. However, specificity of the independent homeodomain protein is not usually enough if I recognize only the required target gene. In most cases, the homeodomain protein acts as a complex with the homeodomain protein that it is often other transcription factors again in the promoter domain of the target gene. Such a complex has the target specificity that is higher than independent homeodomain protein.
The protein including the homeodomain may be greatly classified in two. One comes from the Hox gene cluster forming a characteristic cluster in a genome and is called Hox protein (or merely Hox). It comes from non-Hox gene lying scattered in a genome except Hox one more and is considered to be non-Hox ホメオ protein. Hox gene forms four clusters of the mammals on the different chromosomes, and I am divided into 13 groups by homogeny of the base sequence, and a number is touched by 3' sides. I do the expression along the anterior posterior axis in response to this turn in the developmental process and derive the metamere structure that is characteristic of the position. As for these things, analysis of the homeotic variation of the Drosophila became the beginning.
There are NK-2 family and MSX family, and non-Hox gene knows that these form a family saved evolutionarily about various outbreak differentiation processes. In addition, the MAT gene influencing sex determination of the budding yeast has homeobox.
The Hox gene functions by the pattern formation of the body axis. Therefore I give the identity of the part of the specific body, and the Hox gene decides a limb and other segmental growth in occurring fetus and larvae. Those genetic variation may cause extra growth, and aristapaedia complex typically lets you grow a leg from the place of the feeler of the head because of the loss of one gene of the part of the body which is not functional, e.g., the Drosophila in invertebrates. Variation of the Hox gene in vertebrates usually dies before birth.
Firstly the homeobox gene was found in Drosophilas, and I was identified with reptiles, many other kinds such as mammals successively by an insect. The right figure is the structured model that rat Pit-1 homeobox component protein (purple) connects to DNA. Pit-1 is an adjustment factor of the growth hormone gene transcription. Pit-1 is one of POU DNA-binding domain families of the transcription factor binding to DNA using both POU domain and homeodomain. The homeobox is seen even in fungi and plants such as the yeast of the single cell. As for this, this gene family evolves very early, and morphogenetic basic mechanism shows the same thing in many creatures.
The variation of the homeobox gene produces the changes of the easily visible phenotype. The example of the Drosophila such as the leg in the place of the feeler which I showed at the top and the second pair feather is it. The overlap of the homeobox gene can lay the part of the new body, and there is a possibility that such an overlap is important to the evolution of the animal with the metamere.
It is similar to a computer calculation and can think that the homeobox gene resembles the caller of the subroutine. This becomes the switch of the production of all the subsystems that there has been already in another place of DNA.
Allied item
References
- Lodish et al (2003) Molecular Cell Biology, 5th Edition, New York: W.H. Freeman and Company. ISBN 0716743663
Outside link
- Homeo Box PageThomas R. English site by Bürglin
- Homeobox - brain science dictionary
This article is taken from the Japanese Wikipedia Homeobox
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