Ruddle F H, Bentley K L, Murtha M T, Risch N
Department of Biology, Yale University, New Haven, CT, USA.
Dev Suppl. 1994:155-61.
Homeobox cluster genes (Hox genes) are highly conserved and can be usefully employed to study phyletic relationships and the process of evolution itself. A phylogenetic survey of Hox genes shows an increase in gene number in some more recently evolved forms, particularly in vertebrates. The gene increase has occurred through a two-step process involving first, gene expansion to form a cluster, and second, cluster duplication to form multiple clusters. We also describe data that suggests that non-Hox genes may be preferrentially associated with the Hox clusters and raise the possibility that this association may have an adaptive biological function. Hox gene loss may also play a role in evolution. Hox gene loss is well substantiated in the vertebrates, and we identify additional possible instances of gene loss in the echinoderms and urochordates based on PCR surveys. We point out the possible adaptive role of gene loss in evolution, and urge the extension of gene mapping studies to relevant species as a means of its substantiation.
同源框基因簇（Hox基因）高度保守，可有效地用于研究系统发育关系以及进化过程本身。对Hox基因的系统发育调查显示，在一些最近进化的物种中，尤其是脊椎动物，基因数量有所增加。基因数量的增加是通过两步过程实现的，首先是基因扩张形成一个基因簇，其次是基因簇复制形成多个基因簇。我们还描述了一些数据，这些数据表明非Hox基因可能优先与Hox基因簇相关联，并提出这种关联可能具有适应性生物学功能的可能性。Hox基因丢失也可能在进化中发挥作用。Hox基因丢失在脊椎动物中得到了充分证实，我们基于PCR调查在棘皮动物和尾索动物中发现了基因丢失的其他可能实例。我们指出了基因丢失在进化中可能的适应性作用，并敦促将基因图谱研究扩展到相关物种，以此作为证实这一作用的一种手段。
