Genetic error, sex, and diploidy.
Genetic error, sex, and diploidy.
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遗传错误、性别和二倍体。
DOI：
10.1093/oxfordjournals.jhered.a111357
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
Michod,RE
中科院分区：
文献类型：
--
作者：
Michod,RE
据报道，有关转化的数学模型和实验证实了有性生殖和二倍体作为DNA修复系统进化的假设。这些模型通过研究无性单倍体、有性单倍体和二倍体之间的选择来关注二倍体和有性的起源。单倍体细胞是高效的复制子，而二倍体细胞是抵抗损伤的。有性单倍体可能结合了两者的优点：其生命周期的大部分时间都处于单倍体状态，然后暂时融合成为二倍体，然后分裂成单倍体状态。在二倍体状态下，DNA损伤可以修复，因为细胞中有两个拷贝的基因，其中一个拷贝被推定为未受损。使用了五个基本的比率参数：出生和死亡；基因组损伤(仅针对单倍体)；以及有性细胞的融合和分裂。绘制了平衡点的参数空间分岔图，并用这些分岔图描述了方程的解。每种类型的单元格都有其独占的参数空间区域(给定其在竞争中的初始存在)。单倍体在危害小的环境中获胜。二倍体在危害大、死亡率低、资源丰富的环境中取胜。通常，只有一种类型的单元格占据给定的空间部分。然而，我们发现，无性二倍体和有性单倍体的竞争性共存是可能的，尽管它们竞争的是单一资源(核苷酸构建块)。如果与无性细胞交配，性行为可能会从稀有增加。只有性行为才能同时应对高死亡率和高伤害。然后，我们转向自然细菌转化作为性实验研究的模型系统。自然转化在所有细菌群中广泛分布，但显然很稀少。对细菌及其近缘物种的非常初步的物理发生分析表明，在细菌进化中，转化可能不是一种多样化的力量。然而，由于围绕负面数据的模糊性，这一点很难确定。用枯草芽孢杆菌进行的实验表明，如果使用同源供体DNA，转化频率对DNA损伤的反应是积极的。对于这种反应，我们考虑了几个具体的假设。最近在其他实验室中关于转化进化的工作是从转化在DNA修复中起作用的假设的角度来讨论的。
Mathematical models and experiments on transformation are reported testing the hypothesis that sex and diploidy evolved as a DNA repair system. The models focus on the origin of diploidy and sex by studying selection between asexual haploids, sexual haploids, and diploids. Haploid cells are efficient replicators, while diploid cells are resistance to damage. A sexual haploid may combine the advantages of both: spending much of its life cycle in the haploid state, then temporarily fusing to become diploid, followed by splitting to the haploid state. During the diploid state DNA damage can be repaired, since there are two copies of the gene in the cell and one copy is presumed to be undamaged. Five basic rate parameters are employed: birth and death; genomic damage (for the haploids alone); and, for the sexual cell, fusion and splitting. Parameter space bifurcation diagrams for the equilibria are drawn, and solutions of the equations are described in terms of these diagrams. Each type of cell has a region of the parameter space that it occupies exclusively (given its initial presence in the competition). The haploid wins in environments characterized by low damage. The diploid wins in environments characterized by high damage, low mortality, and abundant resources. In general, only a single type of cell occupies a given portion of the space. We find, however, that competitive coexistence of an asexual diploid and sexual haploid is possible in spite of the fact that they are competing for a single resource (nucleotide building blocks). Sex can increase from rarity if matings occur with asexual cells. Only sex can cope with both high mortality and high damage. We then turn to natural bacterial transformation as a model system for the experimental study of sex. Natural transformation in distributed widely, but apparently sparsely, in all bacterial groups. A very preliminary phy-logenetic analysis of the bacilli and related species indicates that transformation is probably not a diversifying force in bacterial evolution. However, it is difficult to be sure because of the ambiguity surrounding negative data. Experiments with the bacteriumBacillus subtilisindicate that transformation frequencies respond adatively to DNA damage if homologous donor DNA is used. Several specific hypotheses for this response are considered. Recent work in other labs on the evolution of transformation is discussed from the point of view of the hypothesis that transformation functions in a DNA repair.