中文摘要：

脊椎动物在胚胎发育的过程中沿身体前后轴形成一定数目的暂时性结构-体节（semite），随着胚胎的继续发育每个体节分化成为生骨区、生皮区和生肌区，继而生成各种组织。近30年来，研究者们就体节的发生和分化提出了多种解释模型，这包括时钟波峰模型、反应扩散模型、时钟诱导模型、时钟痕迹模型等，这些模型从不同角度不同程度解释了动物体节发生和分化的不同现象。尽管每个模型仍然存在一些不足，但大多提出了时钟分节（segmental clock）这一概念。对鸡的c-hoiry 1和c-heiry 2、鸡和小鼠的I-fng以及斑马鱼的her1和DeltaC等基因的表达图式的研究，为分节时钟的存在提供了分子生物学上的有力证据。

英文摘要：

During embryonic development, many animals form a number of temporary structures along their anteriorposterior axis-somites. Cells in somites differentiate into sclerotome, which gives rise to vertebral column, dermatome, which gives rise to dermis, and myotome, which gives rise to skeletal muscle. During the past three decades, several models have been proposed to explain the formation of somites, including the clock and wavefront model, the reaction-diffusion type model, the clock and induction model, the clock and trail model, and others. These models, albeit not perfect, serve to explain .different aspects of somitogenesis. Most of these models propose the concept of segmental clock. Studies on expression patterns of c-hairy 1 and c-hairy 2 in chick, I-fng in chick and mouse, and her 1 and Delta C in zebrafish have provided evidence for the existence of segmental clock.