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An extension of neo-Darwinism, termed preassembly, states that genetic material required for many complex traits, such as echolocation, was present long before emergence of the traits. Assembly of genes and gene segments had occurred over protracted time-periods within large libraries of non-coding genes. Epigenetic factors ultimately promoted transfers from noncoding to coding genes, leading to abrupt formation of the trait via de novo genes. This preassembly model explains many observations that to this present day still puzzle biologists: formation of super-complexity in the absence of multiple fossil precursors, as with bat echolocation and flowering plants; major genetic and physical alterations occurring in just a few thousand years, as with housecat evolution; lack of precursors preceding lush periods of species expansion, as in the Cambrian explosion; and evolution of costly traits that exceed their need during evolutionary times, as with human intelligence. What follows in this paper is a mechanism that is not meant to supplant neo-Darwinism; instead, preassembly aims to supplement current ideas when complexity issues leave them struggling. 相似文献
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表观遗传修饰是指在不改变DNA序列的情况下,基因表达发生的可遗传变化.5-羟甲基胞嘧啶(5-hydroxymethylcytosine, 5hmC)是继5-甲基胞嘧啶(5-methylcytosine, 5mC)后发现的表观遗传修饰,被称为\"第六种碱基\". 5hmC广泛分布于哺乳动物的组织和细胞中,它的异常表达与肿瘤发生、发育性疾病和神经系统疾病密切相关.由于5hm C的结构与5m C相似,并且其丰度远远低于5m C,传统方法难以实现对5hm C的准确和灵敏检测.近年来,科学家们结合新的修饰方法和信号放大策略,发展了一系列超灵敏检测5hm C的新方法,包括液相色谱串联质谱法、荧光法、电化学法、光电化学法、单碱基分辨率的测序法和单分子检测技术.这些方法各自具有其独特优势,有力推动了表观遗传学的发展.本综述总结了5hmC检测方法的最新研究进展,并对其面临的挑战和发展趋势做了展望. 相似文献
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