摘要
基因组记录着物种的全套核苷酸序列信息,其大小与物种进化地位之间的关系由于"C值悖论"的提出而引人关注.本文回顾了关于基因组大小研究的历史,简述了基因组大小和细胞性状及自身组成之间关系的研究进展及相关假设,并在不同分类尺度上分析了影响基因组大小进化的可能因素.我们认为随着进化地位的提高和相应的遗传信息量增加,基因组大小有增加的内在必然性;但是在真核生物中,随着基因组的增大,增加的DNA逐渐由基因序列转变为主要是内含子和基因间区等非编码DNA序列,而非编码序列的大量增加并不明显改变物种的进化地位,却在很大程度上掩盖了基因组大小与物种进化复杂度之间的相关性,从而导致了C值悖论.我们认为分子突变导致了基因组大小的变化,而自然选择对保留有益的变化起到了重要的作用.
A genome is a set of DNA sequences encoding the complete genetic information of an organism, therefore more complex organisms are reasonably expected to have larger genomes. However, eukaryotic genome size vary drastically and seems to have no connection to the evolutionary complexity. Such an inconsistency between them is known as the C-value paradox. Here we briefly introduced the history of researches on genome size, and reviewed the advances and hypotheses of the researches on the relationships between genome size and evolutionary level, genome composition and some cell traits. At the top level of biological classification, the increase of evolutionary complexity is notably coupled with the augment of genetic information which leads to bigger genome sizes. Albeit there are overlapping between adjacent groups, the genome sizes rank upwards as evolutionary complexity, i.e, viruses〈prokaryotes〈eukaryotes. The genome size correlates with some cell traits, such as cell size, mobility, the rate of cell division, or even the rate of embryo development. One presumption is that the coordinated variation of cell traits and genome size was resulted by evolutionary pressure, and the alternative explanation is that the endogenous growth of DNA led to consequent variations in cell size or other cell traits. The genome composition changes accordingly with the genome size. With the enlargement of eukaryotic genomes, the increments gradually shift from coding DNA sequences to noncoding DNA sequences, which includes introns and intergenic regions. Since genes are the most crucial molecular bases for the physiological functions and gene number determines the complexity of molecular network in a cell, we conjecture that gene number positively correlates to organism＇s evolutionary complexity. On the other hand, the introduction of noncoding DNA regions provides more cis-regulatory element sites, more alternative splicing genotypes, and higher allele exchange frequency, therefore endows a population higher genetic diversity
作者
石米娟
程莹寅
张婉婷
夏晓勤
SHI MiJuan CHENG YingYin ZHANG WanTing XIA XiaoQin(Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, Chin)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2016年第30期3188-3195,共8页
Chinese Science Bulletin
