School of Life and Health Sciences, University of Delaware, Newark, Delaware.
Genetics. 1980 Sep;96(1):125-36. doi: 10.1093/genetics/96.1.125.
Previous work has shown that genetic exchange occurs in the macrocyst of Polysphondylium pallidum, as in species of Dictyostelium. These studies are extended here. Mutants resistant to six different poisons have been isolated for use as genetic markers. A replica-plating technique has been engineered whereby 14 progeny clones growing on a master plate may be simultaneously transferred to test plates containing individual poisons. Germination percent of macrocysts has been greatly increased by the presence of a growing fungus during the resting stage. These means have been used to analyze crosses showing that: (1) Vegetative amebae are haploid, at least at the three marker loci tested. (2) Amebae emerging from a single macrocyst are identical about 90% of the time. (3) Any single combination of parental markers may emerge from a given macrocyst, and all combinations appear in approximately equal frequencies. These findings suggest that normally one of four nuclei produced by meiosis survives in every macrocyst and that all markers examined are unlinked. (4) About 10% of the macrocysts germinate to give two or more classes of progeny. These may result from the presence of a second zygote in the macrocyst or from the survival of two nuclei after meiosis. (5) If genetic exchange occurs during spore formation or microcyst formation, its frequency is low (<0.01%).
先前的工作表明，多核粘菌中的遗传交换与双细胞粘菌属的物种相同。本文对这些研究进行了扩展。已经分离出对六种不同毒物具有抗性的突变体，用作遗传标记。设计了一种复制平板技术，通过该技术，可以将在主平板上生长的 14 个后代克隆同时转移到含有单个毒物的测试平板上。在休眠阶段存在生长的真菌时，多核粘菌的萌发率大大提高。这些方法已用于分析表明：（1）营养变形虫至少在三个标记基因座中是单倍体。（2）从单个多核粘菌中出现的变形虫大约有 90%的时间是相同的。（3）任何一对亲本标记都可能出现在给定的多核粘菌中，所有组合出现的频率大致相等。这些发现表明，正常情况下，减数分裂产生的四个核中有一个存活在每个多核粘菌中，并且所有检查的标记都不连锁。（4）大约 10%的多核粘菌萌发产生两个或更多类别的后代。这些可能是由于多核粘菌中有第二个合子存在，或者是减数分裂后两个核存活的结果。（5）如果在孢子形成或小囊形成过程中发生遗传交换，其频率很低（<0.01%）。
