四膜虫接合过程中旧大核内基因的彻底降解

形态学和遗传学方法早巳证明四膜虫接合过程中旧大核退化消失,其基因型对接合后代不发生影响。本文以1种具有强大复制优势而且是抗药性的rDNA分子,rdna-A3,为指标,证明在接合过程中旧大核内上万个rDNA分子没有1个能进入新大核,从而在基因分子水平上证明旧大核的退化是极为彻底的。同时检测了接合过程中旧大核内DNA发生降解的时间。

Complete Degradation of Old Macronuclear Genome During Conjugation of Tetrahymena

It i$ previously known by both morphology and genetics that the old macronucleus degenerates during conjugation of Tetrahymena and its genome makes no contribution to new generation (F1). Taking advantage of a rDNA mutant, rdna-A3, which is of paromomycin resistance marker and has replication predominance over wild type rdna , we demonstrated that among 10 000 copies of rDNA in the old macronucleus none could "leak" into the developing new macromucleus during conjugation. It was therefore confirmed at the level of gene-molecules that the degeneration of old macronuclear genome is absolutely complete. The timing of DNA degradation in old macromucleus during conjugation was examined.