Homeobox Genes and Evolutionary Innovation

9507466最近发现的控制动物身体计划发育的基因(同源盒基因)为解决生物学中最基本的问题之一提供了机会。也就是说，是什么机制导致了新角色或身体计划的出现，这些新角色或身体计划表征了生物多样性中的主要辐射？我们知道物种如何通过修改给定的身体计划来适应环境变化，但我们还不知道特定的身体计划最初是如何产生的。例如，青蛙与相关的两栖动物的不同之处在于，它们的两块脚踝骨骼都被大大拉长，从而提高了跳跃能力。这项研究将检验一种假设，即同源框基因表达的变化导致了这种形态创新。它将研究青蛙肢体中基因的表达，这些基因在其他脊椎动物中控制着小腿(长骨)和脚踝(通常是短骨)的分化。结果将显示，在青蛙的脚踝骨骼伸长过程中，导致小腿伸长的基因是否活跃，但在其他脊椎动物中是否不活跃。如果是这样的话，这将表明脊椎动物的特征可以通过改变几个发育控制基因的表达来经历重大的进化变化。这一结果可能会增加对遗传机制、进化史的理解，并解释某些形态创新在化石记录中迅速出现的原因。

9507466 The recent discovery of genes controlling the development of the animal body plan (homeobox genes) provides an opportunity to address one of the most fundamental questions in biology. That is, what mechanisms have led to the appearance of new characters or body plans that characterize major radiations in biological diversity? We understand how species adapt to environmental changes by modifying a given body plan, but we do not yet understand how a particular body plan came into existence in the first place. For example, frogs differ from related amphibians in having two ankle bones that are greatly elongated, improving jumping ability. This research will test the hypothesis that changes in expression of homeobox genes led to this morphological innovation. It will study the expression of genes in the frog limb that, in other vertebrates, control the differentiation into lower leg (long bones) and ankle (usually short bones). The results will show whether the gene responsible for lower leg elongation is active during elongation of the ankle bones of frogs, but not in other vertebrates. If so, it will show that a vertebrate character can undergo a major evolutionary change via alteration in the expression of a few developmental control genes. The results could increase understanding of genetic mechanisms, of evolutionary history and account for the rapid appearance of certain morphological innovations in the fossil record.