Growth, Mutation and Recombination in Bacteriophage

噬菌体的生长、突变和重组

• 批准号: 9402695
• 负责人: Franklin Stahl
• 金额: $ 85万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-09-01 至 2000-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9402695&HistoricalAwards=false
• 关键词: Growth; Mutation; Recombination; Bacteriophage

Abstract 9402695 In crosses involving either pro- or eukaryotes, genetic exchanges may be nonrandomly distributed with respect to each other, i.e., they may show "interference." The investigation of two systems in which interference is manifest will continue. In both systems, interference may depend on a "machine" that moves along chromosomes. Understanding of these machines will contribute to our understanding of molecular mechanisms of genetic recombination. (1) When the RecBCD recombination pathway of E. coli operates on phage lambda carrying the recombination hot spot Chi, recombinant chromosomes recovered in phage particles have sometimes indulged in a pair of exchanges, one reciprocal and one not. The nonreciprocal exchange occurs not at random but to the right of the reciprocal one on the standard lambda linkage map. The basis for this nonrandom relationship resides in the RecBCD protein, which enters DNA at a double-chain break and travels destructively along the duplex, changing from an exonuclease to a "recombinase" when it encounters the sequence 5'GCTGGTGG3' (Chi). Models for the mechanisms of the two exchanges and for the relationship between them are being tested. (2) In many eukaryotes, the presence of one exchange in a meiotic bivalent reduces the probability of finding an exchange in nearby intervals (chiasma interference). A simple model that unites observations on gene conversion with those on chiasma interference has been developed. The model supposes that conversions occur at random with respect to each other, but that those with associated crossing over are invariably separated by several conversions that lack associated crossing over. Thus, the two kinds of recombination events(one of which is sometimes called "reciprocal" and the other not) are nonrandomly distributed with respect to themselves and each other. Development of the model and testing of it continues. Hypotheses regarding mechanisms underlying the model are being te sted. Such mechanisms may involve a "machine" that travels along the synaptonemal complex resolving double-chain break-repair intermediates such that a fixed number of repair events unaccompanied by crossing over fall between neighboring crossovers. %%% Recombination occurs in almost all organisms, and is responsible for leading to new combinations of genes in offspring as well as protection against damage to DNA and genes. A better understanding of this process should be applicable to many organisms, and could lead to the development of better ways of introducing foreign genes into organisms ("genetic engineering"). ***

在涉及原核生物或真核生物的杂交中，遗传交换可以相对于彼此非随机地分布，即， 它们可以显示“干扰”。“对两个明显存在干扰的系统的调查将继续进行。 在这两个系统中，干扰可能取决于一个“机器”，沿着沿着移动。 了解这些机器将有助于我们理解基因重组的分子机制。 (1)当E.当大肠杆菌在携带重组热点Chi的λ噬菌体上运行时，在噬菌体颗粒中回收的重组染色体有时会进行一对交换，一个是相互的，一个不是。 在标准λ连锁图上，非互惠交换不是随机发生的，而是发生在互惠交换的右边。 这种非随机关系的基础在于RecBCD蛋白，它在双链断裂时进入DNA，并沿着双链体破坏性地沿着行进，当遇到序列5 'GCTGGTGG 3'（Chi）时，从核酸外切酶转变为“重组酶”。 目前正在测试两个交流机制和它们之间关系的模式。 (2)在许多真核生物中，减数分裂二价体中一个交换的存在降低了在附近间隔中发现交换的概率（交叉干扰）。 一个简单的模型，结合观察基因转换与交叉干扰已经开发出来。 该模型假设转换相对于彼此随机发生，但是那些具有相关交换的转换总是被几个缺乏相关交换的转换分开。 因此，这两种重组事件（其中一种有时被称为“互惠”，另一种则不是）相对于它们自己和彼此是非随机分布的。 模型的开发和测试工作仍在继续。 关于该模型的机制的假设正在测试中。 这样的机制可能涉及一个“机器”，该机器沿着联会复合体行进，解析双链断裂-修复中间体，使得固定数量的修复事件不伴随着相邻交叉之间的交叉。 几乎所有的生物体都会发生突变，这种突变会导致后代中新的基因组合，并保护DNA和基因免受损伤。 更好地理解这一过程应该适用于许多生物体，并可能导致开发更好的方法将外源基因引入生物体（“基因工程”）。 ***