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Paper Topic:

Discuss how homeotic genes control development in vertebrates






Discussion of how homeotic genes control development in vertebrates


Homeotic genes which are found in the fruit fly Drosophila are involved in pattern formation during embryonic development . As based on the sequence similarities more than thirty homeo box-containing genes of the class Antenntapaedia have been identified in mouse as well as man . The genomic organization of this multigene family in gene clusters located on different chromosomes supports the hypothesis that the homeo box gene complexes evolved by duplications . The cluster duplications

can be argued that they happened early during vertebrate evolution . As one base on the comparison of the arthropod as well as vertebrate homeo box gene systems , he considers the function of multi - gene regulatory networks for the specifications of the regional as well as cellular identify during development and in the regional as well as cellular identity during development and in the adult organism . It can be argued that during evolution the homeo box gene network may have been crucially involved in the development of new body plans and behavioral attributes (Daston , 2005 ,



The homeo box was first discovered as a common DNA sequences element in home genes of the fruit -fly Drosophila melanogastor . These genes normally regulate the development and morphogenesis of the fly - as well as mutations in such genes lead to characteristic phenotypes , so-called homeotic transformations , for example , the transformation of antennae into legs . Homeo box genes have subsequently been isolated form a variety of organisms including chicken , frogs , mice as well as humans (Daston , 2005 ,


They can normally be grouped into different categories based on their sequences as well as their biological features . Homeo domains have been identified in ubiquitous transcription factors such as Oct . -1 , and in tissue - specific transcription factors . Examples for the latter one Pit - l ,a pituitary - specific transcription activator of the gene for growth homeo and Oct - 2 that regulates the transcriptional activity of immunoglobulin genes . These are genes of the so-called class Antennapaedia are the Drosophila homeotic genes , and it is this similarity that suggest that they may also ply a crucial role in development in vertebrate (Leroy , 2003 ,


Expression of mammalian homeo box genes

The homeo box genes in vertebrates are typically about 10kb (kilo bases ) long as well as consist of at least two exons . The genes encode proteins of the average size of 240 amino acids . Normally the homeo domain resides in the carboxy - terminal part of these proteins . The hexapeptide sequence has been implicated such that it mediates dimerization of home demean proteins (Jenkins , 2000 ,

.372 ) The expression patterns of homeo box genes are quite complex and of late been covered extensively . The most interesting feature of the expression patterns of class Antennapaedia homeo box genes in developing embryos in the region specific accumulation of their respective mRNAs Each homeo box genes has a characteristic anterior boundary of expression in the spinal cord , and while the posterior boundary is less...

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