Reanney D C
Int Rev Cytol. 1974;37(0):21-52. doi: 10.1016/s0074-7696(08)61356-x.
This chapter discusses the role of viruses in nature. Viral transduction of structural and regulatory genes provides a means for information to leave the body of an organism other than through the germ cells. Natural selection acts upon the cell–virus nucleic acid coupling and the rate and direction of the evolution of any species depends upon the number of associated viruses and the extent to and speed with which they allow information to be cycled through the total gene pool of that population. There are three mechanisms by which gene material can be transferred from cell to cell: (1) transformation, (2) transduction, and (3) sexual conjugation. Transformation is the most random and inefficient process; it requires the laws of diffusion and the existing chemistry of the cell membrane, modified in contemporary cells by the development of transport systems, which facilitate membrane penetration. Transduction requires the development of genes for capsomere proteins to encapsidate nucleic acid and a sophistication of the process of membrane evagination to package nucleic acid into free particles, These are relatively modest genetic adaptations. However, true sexual union as it occurs in modern eukaryotes, requires such a high degree of cytological organization that it is inconceivable that it could have operated efficiently during the first billion or so years of cell evolution.
本章讨论病毒在自然界中的作用。结构基因和调控基因的病毒转导为信息提供了一种途径，使其能够通过除生殖细胞之外的生物体的身体离开。自然选择作用于细胞 - 病毒核酸偶联，任何物种进化的速率和方向取决于相关病毒的数量以及它们允许信息在该种群的整个基因库中循环的程度和速度。基因物质可以通过三种机制从一个细胞转移到另一个细胞：（1）转化，（2）转导，以及（3）有性接合。转化是最随机且效率最低的过程；它需要扩散定律和细胞膜的现有化学性质，在当代细胞中通过运输系统的发展进行了修饰，这些运输系统促进了膜的穿透。转导需要为衣壳蛋白编码的基因的发展，以便包裹核酸，并且需要复杂的膜内陷过程将核酸包装成游离颗粒，这些都是相对适度的遗传适应。然而，现代真核生物中发生的真正有性结合需要如此高度的细胞学组织，以至于在细胞进化的最初大约十亿年中它不可能有效地运作，这是不可思议的。
