Jackson J A, Fink G R
Genetics. 1985 Feb;109(2):303-32. doi: 10.1093/genetics/109.2.303.
We have studied the meiotic recombination behavior of strains carrying two types of duplications of an 18.6-kilobase HIS4 Bam HI fragment. The first type is a direct duplication of the HIS4 Bam HI fragment in which the repeated sequences are separated by Escherichia coli plasmid sequences. The second type, a tandem duplication, has no sequences intervening between the repeated yeast DNA. The HIS4 genes in each region were marked genetically so that recombination events between the duplicated segments could be identified. Meiotic progeny of the strains carrying the duplication were analyzed genetically and biochemically to determine the types of recombination events that had occurred. Analysis of the direct vs. tandem duplication suggests that the E. coli plasmid sequences are recombinogenic in yeast when homozygous. In both types of duplications recombination between the duplicated HIS4 regions occurs at high frequency and involves predominantly interchromosomal reciprocal exchanges (equal and unequal crossovers). The striking observation is that intrachromosomal reciprocal recombination is very rare in comparison with interchromosomal reciprocal recombination. However, intrachromosomal gene conversion occurs at about the same frequency as interchromosomal gene conversion. Reciprocal recombination events between regions on the same chromatid are the most infrequent exchanges. These data suggest that intrachromosomal reciprocal exchanges are suppressed.
我们研究了携带18.6千碱基HIS4 Bam HI片段两种重复类型的菌株的减数分裂重组行为。第一种类型是HIS4 Bam HI片段的直接重复，其中重复序列被大肠杆菌质粒序列隔开。第二种类型是串联重复，在重复的酵母DNA之间没有间隔序列。每个区域的HIS4基因通过遗传标记，以便能够识别重复片段之间的重组事件。对携带重复片段的菌株的减数分裂后代进行了遗传和生化分析，以确定发生的重组事件类型。对直接重复与串联重复的分析表明，大肠杆菌质粒序列在纯合时在酵母中具有重组活性。在两种重复类型中，重复的HIS4区域之间的重组都以高频率发生，并且主要涉及染色体间的相互交换（相等和不相等的交叉）。引人注目的观察结果是，与染色体间相互重组相比，染色体内相互重组非常罕见。然而，染色体内基因转换的发生频率与染色体间基因转换大致相同。同一染色单体上区域之间的相互重组事件是最不常见的交换。这些数据表明染色体内相互交换受到抑制。
