Hamza H, Kalogeropoulos A, Nicolas A, Rossignol J L
Proc Natl Acad Sci U S A. 1986 Oct;83(19):7386-90. doi: 10.1073/pnas.83.19.7386.
G234 is a large silent deletion located in the middle of gene b2, which controls spore pigmentation in Ascobolus immersus. Its gene conversion directionality was studied in asci, which show evidence of heteroduplex DNA at flanking markers, and was compared to the behavior of closely linked single-base-pair insertions or deletions. We found that with the G234 deletion, the genotype of the donor strand in the heteroduplex is preferentially recovered, irrespective of its G234 or wild-type nature, whereas with single-base-pair insertions or deletions, the direction of conversion favors one genotype, whether it was the donor or the recipient strand. We conclude that there exists two mechanisms for directional gene conversion, the "donor-directed" conversion mechanism being epistatic to the "genotype-directed" one. We discuss these data with regard to models for mismatch repair.
G234是一个位于基因b2中间的大片段沉默缺失，该基因控制浸没状粪壳菌的孢子色素沉着。在子囊中研究了其基因转换方向性，子囊在侧翼标记处显示出异源双链DNA的证据，并将其与紧密连锁的单碱基对插入或缺失的行为进行了比较。我们发现，对于G234缺失，异源双链中供体链的基因型优先恢复，无论其是G234还是野生型性质，而对于单碱基对插入或缺失，转换方向有利于一种基因型，无论它是供体链还是受体链。我们得出结论，存在两种定向基因转换机制，“供体定向”转换机制对“基因型定向”机制具有上位性。我们根据错配修复模型讨论了这些数据。
