Sequential functions of the bithorax complex of Drosophila
Sequential functions of the bithorax complex of Drosophila
复制标题
果蝇双胸复合体的序列功能
作者：
G. Morata;S. Kerridge
双胸基因是果蝇中一组同源异型基因，其功能与控制体节发育有关。它们形成一个基因复合体，其中至少有7个不同的基因座已被确定1 -3。在这些基因座的每一个突变产生一个特定的同源异型转化，其中一个片段被部分或完全转化成另一个片段3 -5。在双胸基因完全缺乏的胚胎中，所有的胸段和腹段都类似于中胸段3。这一观察结果，连同突变表型的片段特异性，导致Lewis提出了一种遗传控制模型，其中每个片段的发育类型由双胸基因总数的一部分的激活来指定。因此，双胸基因活性的缺乏导致中胸的发育，双胸（bx+）和后双胸（pbx+）基因的激活产生后胸（分别为前胸和后胸），而这两个基因与双胸（bxd+）的激活产生第一腹节等等。我们现在描述两个意想不到的结果：双胸基因的缺陷会导致片段转化为前胸，并且双胸系统的功能存在时间序列。
The bithorax genes are a group of homoeotic genes of Drosophila whose function is related to the control of segment development. They form a gene complex in which at least seven different loci have been identified1–3. Mutations at each of these loci produce a specific homoeotic transformation whereby a segment is transformed either in part or completely into another3–5. In embryos completely deficient for the bithorax genes, all the thoracic and abdominal segments resemble mesothoracic segments3. This observation, together with the segmental specificity of the mutant phenotypes, led Lewis3 to suggest a model of genetic control in which the type of development in each segment is specified by the activation of a fraction of the total number of bithorax genes. Thus, lack of activity of the bithorax genes results in mesothoracic development, activation of the bithorax (bx+) and postbithorax (pbx+) genes produces metathorax (anterior and posterior respectively), and activation of these two genes with bithoraxoid (bxd+) produces the first abdominal segment and so on. Although this model explains the genetic and developmental data, it leaves unexplained formation of the prothoracic segment. We now describe two unexpected results: deficiencies for bithorax genes can lead to segments being transformed into prothorax, and there is a temporal sequence in the function of the bithorax system.