Animal Genomics and Bioresource Research Center (AGB Research Center), Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand.
Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand.
Cells. 2021 Aug 24;10(9):2182. doi: 10.3390/cells10092182.
With more than 70,000 living species, vertebrates have a huge impact on the field of biology and research, including karyotype evolution. One prominent aspect of many vertebrate karyotypes is the enigmatic occurrence of tiny and often cytogenetically indistinguishable microchromosomes, which possess distinctive features compared to macrochromosomes. Why certain vertebrate species carry these microchromosomes in some lineages while others do not, and how they evolve remain open questions. New studies have shown that microchromosomes exhibit certain unique characteristics of genome structure and organization, such as high gene densities, low heterochromatin levels, and high rates of recombination. Our review focuses on recent concepts to expand current knowledge on the dynamic nature of karyotype evolution in vertebrates, raising important questions regarding the evolutionary origins and ramifications of microchromosomes. We introduce the basic karyotypic features to clarify the size, shape, and morphology of macro- and microchromosomes and report their distribution across different lineages. Finally, we characterize the mechanisms of different evolutionary forces underlying the origin and evolution of microchromosomes.
具有超过 70,000 个现存物种，脊椎动物对生物学和研究领域具有巨大影响，包括核型进化。许多脊椎动物核型的一个突出方面是微小的、通常在细胞遗传学上无法区分的微染色体的神秘出现，与大染色体相比，这些微染色体具有独特的特征。为什么某些脊椎动物物种在某些谱系中携带这些微染色体，而其他谱系则不携带，以及它们如何进化仍然是悬而未决的问题。新的研究表明，微染色体表现出某些独特的基因组结构和组织特征，例如高基因密度、低异染色质水平和高重组率。我们的综述重点关注最近的概念，以扩展对脊椎动物核型进化动态性质的现有认识，提出有关微染色体进化起源和影响的重要问题。我们介绍了基本的核型特征，以澄清大染色体和微染色体的大小、形状和形态，并报告它们在不同谱系中的分布。最后，我们描述了不同进化力量在微染色体起源和进化中的作用机制。
