Cells at different distances from the zone of polarizing activity are exposed to different concentrations of the morphogens and respond differently. Studies of Drosophila melanogaster have provided a great deal of information about the development of body segmentation . A gene cascade controls segmentation and pattern formation in Drosophila. The product of one gene promotes or represses the expression of another gene, and so on. Activation of segmentation genes leads to activation of homeotic genes in different segments.
Homeotic genes define the functional characteristics of the segments.
Homeotic genes contain the homeobox , which encodes an amino acid sequence that is part of many transcription factors. The homeobox is a 180 base pair sequence and is found in many species. The homeobox is found in key genes of distantly related species suggesting that numerous regulatory mechanisms may trace back to a single evolutionary precursor. Chapter 16 Recombinant DNA and Biotechnology Recombinant DNA and biotechnology used to manipulate DNA are important areas of research and practical application in today's society. In the last two decades, tremendous advances have been made in these areas.