The evolution of the avian genome as revealed by comparative molecular cytogenetics
The evolution of the avian genome as revealed by comparative molecular cytogenetics
复制标题
DOI：
10.1159/000103166
复制
发表时间：
2007-01-01
影响因子：
1.7
通讯作者：
Skinner, B. M.
中科院分区：
文献类型：
--
作者：
Griffin, D. K.;Robertson, L. B. W.;Skinner, B. M.
鸟类的特征是羽毛，飞行，小基因组和非常独特的核型。尽管有大量的染色体，2n的二倍体计数接近80一直保持显著恒定，63%的鸟类2n = 74-86，24%的鸟类2n = 66-74，极端的2n = 40和2n = 142。其中，研究最多的是鸡（2n = 78），从这个物种产生的分子细胞遗传学探针已被用于进一步了解鸟类基因组的进化。祖先的染色体组型似乎与鸡的非常相似，鸡的染色体1、2、3、4 q、5、6、7、8、9、4 p和Z代表祖先的鸟类染色体1-10 + Z;染色体4是最古老的。鸟类的进化主要经历了三个阶段：以现存平胸类（鸸鹋、鸵鸟等）为代表的类群分化;从其余;分歧的Galloanserae（鸡，火鸡，鸭，鹅等）- 研究最多的类群;以及“陆地”和“水域”高等鸟类的分歧。除了第一次分化中的性染色体分化外，没有与任何这些进化里程碑相关的特定变化，尽管某些科和目经历了多次融合（和一些分裂），这减少了它们的染色体数量; Falconiformes是最好的描述。总的来说，大多数变化似乎涉及染色体1、2、4、10和Z，其中Z变化是染色体内的;也有一些重复（会聚）事件。其中，最令人困惑的是4号和10号染色体，它们似乎在整个进化过程中经历了多次分裂和/或融合-三种可能的假设被提出来解释这些发现。最后，我们推测这些染色体的奇怪行为的原因，以及端粒和细胞核组织在鸟类进化中的作用。版权所有（c）2007 S. Karger AG，巴塞尔
Birds are characterised by feathers, flight, a small genome and a very distinctive karyotype. Despite the large numbers of chromosomes, the diploid count of 2n approximate to 80 has remained remarkably constant with 63% of birds where 2n = 74-86, 24% with 2n = 66-74 and extremes of 2n = 40 and 2n = 142. Of these, the most studied is the chicken ( 2n = 78), and molecular cytogenetic probes generated from this species have been used to further understand the evolution of the avian genome. The ancestral karyotype is, it appears, very similar to that of the chicken, with chicken chromosomes 1, 2, 3, 4q, 5, 6, 7, 8, 9, 4p and Z representing the ancestral avian chromosomes 1-10 + Z; chromosome 4 being the most ancient. Avian evolution occurred primarily in three stages: the divergence of the group represented by extant ratites ( emu, ostrich etc.) from the rest; divergence of the Galloanserae ( chicken, turkey, duck, goose etc.) - the most studied group; and divergence of the 'land' and 'water' higher birds. Other than sex chromosome differentiation in the first divergence there are no specific changes associated with any of these evolutionary milestones although certain families and orders have undergone multiple fusions ( and some fissions), which has reduced their chromosome number; the Falconiformes are the best described. Most changes, overall, seem to involve chromosomes 1, 2, 4, 10 and Z where the Z changes are intrachromosomal; there are also some recurring ( convergent) events. Of these, the most puzzling involves chromosomes 4 and 10, which appear to have undergone multiple fissions and/or fusions throughout evolution - three possible hypotheses are presented to explain the findings. We conclude by speculating as to the reasons for the strange behaviour of these chromosomes as well as the role of telomeres and nuclear organisation in avian evolution. Copyright (c) 2007 S. Karger AG, Basel