Rates Of Spontaneous Mutation

工作总结：生物体之间的自发突变率差异很大。我们以前描述了几个基因组突变率是某些广泛的生物体群体的特征。(1)基于DNA的微生物的特征突变率为每次基因组复制约0.003。问题是，这种速率是否也发生在包括太古代在内的极端微生物中。我们的特点是突变过程中生长在pH值3.5，在75？C.测量的速率0.002与特征值没有差异。这种生物中碱基对替换的比例低于所有其他基于DNA的生物。(2)利用在携带TMV转基因的宿主中生长的烟草花叶病毒获得了核糖病毒的第一个突变谱，该TMV转基因补充了804碱基基因中的缺陷，该基因有利于病毒颗粒在细胞之间的传播。最值得注意的方面是携带多个突变的突变体的高比例，远远超过基于突变频率的预测。结果表明，非遗传性的，短暂的超变发生在病毒繁殖的时间。

Summary of Work: Rates of spontaneous mutation vary greatly among organisms. We have previously described several genomic mutation rates that are characteristic of certain broad groups of organisms. (1) The characteristic mutation rate for DNA-based microbes is about 0.003 per genome replication. The question arises whether this rate also occurs in extremophiles including Archeons. We have characterized the mutation process in the Archeon Sulfolobus acidocaldarius growing at pH 3.5 at 75?C. The measured rate, 0.002, is not different from the characteristic value. The proportion of base-pair substitutions in this organism is lower than in all other DNA-based organisms. (2) The first mutational spectrum for a ribovirus has been obtained using tobacco mosaic virus growing in a host carrying a TMV transgene that complements defects in the 804-base gene that facilitates the spread of virus particles between cells. The most remarakable aspect of the spectrum is the high proportion of mutants carrying multiple mutations, far in excess of predictions based on the mutant frequency. The results suggest that nonheritable, transitory hypermutability occurs from time to time during virus reproduction.