Hohmann S, Gozalbo D
Institut für Mikrobiologie, Technische Hochschule Darmstadt, F.R.G.
Mutat Res. 1989 Nov;215(1):79-87. doi: 10.1016/0027-5107(89)90220-0.
The nucleotide sequences of closely related members of a gene family can be used to investigate spontaneous mutations. Here we analyse the sequences of different yeast invertase genes which are more than 93% identical in the coding region and share some very similar, but not identical sequences in the noncoding flanking regions. Since all except one of the invertase genes are active, most of the base substitutions are silent. Within the coding region the base substitutions are unevenly distributed, indicating that parts of the genes were homogenized, probably via gene conversion. Transitions occurred more frequently than transversions in both, coding and noncoding regions. In the coding region pyrimidine transitions were the most abundant event due to silent changes mainly in the third codon position. In the noncoding region pyrimidine and purine transitions were found at equal frequencies. Transversions inverting base pairs (A-T and G-C) outnumber transversions changing base pairs (A-C and G-T). While the spectrum of mutations in the coding region is influenced by selective pressure to maintain the amino acid sequence, the spectrum in the noncoding region may be much less affected by selective pressure.
基因家族中密切相关成员的核苷酸序列可用于研究自发突变。在此，我们分析了不同酵母转化酶基因的序列，这些基因在编码区的同一性超过93%，并且在非编码侧翼区共享一些非常相似但不完全相同的序列。由于除一个转化酶基因外其他所有基因都是有活性的，所以大多数碱基替换都是沉默的。在编码区内，碱基替换分布不均，这表明基因的某些部分可能通过基因转换实现了同质化。在编码区和非编码区，转换都比颠换更频繁发生。在编码区，由于主要在密码子第三位的沉默变化，嘧啶转换是最常见的事件。在非编码区，嘧啶和嘌呤转换的频率相等。颠倒碱基对（A-T和G-C）的颠换数量多于改变碱基对（A-C和G-T）的颠换。虽然编码区的突变谱受到维持氨基酸序列的选择压力的影响，但非编码区的突变谱可能受选择压力的影响要小得多。
