Ellegren Hans
Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden.
Trends Ecol Evol. 2005 Apr;20(4):180-6. doi: 10.1016/j.tree.2005.01.015.
Our knowledge of avian genomics has increased rapidly over the past few years, culminating in the recent publication of a draft sequence of the chicken genome, a milestone event in avian genetics and evolutionary biology. Comparative analysis reveals a compact avian genome structure containing a similar number of genes as found in mammals but with shorter intergenic DNA sequences and fewer repeats. Recombination is at a higher rate than in mammals, particularly for microchromosomes. These also differ from macrochromosomes in their GC and gene content, and their substitution rate. The avian genome has remained unusually stable during evolution and contrasts sharply with the frequent chromosomal rearrangements seen in the rodent lineage. Detailed analyses of polymorphism levels in chickens, including a genome-wide screening in three chicken breeds yielding a set of 2.8 million SNP markers, reveal unexpectedly high levels of genetic diversity. As a notable exception, the female-specific W chromosome is very low in diversity, a probable consequence of the effect of selection on non-recombining chromosomes. The chicken genome promises to be a useful resource for ecological and evolutionary studies of other bird species.
在过去几年里，我们对鸟类基因组学的了解迅速增加，最近鸡基因组序列草图的发表达到了顶峰，这是鸟类遗传学和进化生物学中的一个里程碑事件。比较分析揭示了一种紧凑的鸟类基因组结构，其基因数量与哺乳动物相似，但基因间DNA序列较短且重复序列较少。重组率高于哺乳动物，尤其是对于微染色体而言。微染色体在GC含量、基因含量及其替代率方面也与大染色体不同。鸟类基因组在进化过程中一直保持着异常的稳定性，这与啮齿动物谱系中频繁的染色体重排形成了鲜明对比。对鸡多态性水平的详细分析，包括对三个鸡品种进行全基因组筛选，产生了一组280万个单核苷酸多态性（SNP）标记，结果显示出意外高的遗传多样性水平。作为一个显著的例外，雌性特异性W染色体的多样性非常低，这可能是选择作用于非重组染色体的结果。鸡基因组有望成为研究其他鸟类物种生态和进化的有用资源。
