RATE OF PHENOTYPIC ASSORTMENT IN TETRAHYMENA-THERMOPHILA
RATE OF PHENOTYPIC ASSORTMENT IN TETRAHYMENA-THERMOPHILA
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DOI：
10.1002/dvg.1020130206
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发表时间：
1992-01-01
期刊：
影响因子：
--
通讯作者：
LIEF, JH
中科院分区：
文献类型：
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作者：
DOERDER, FP;DEAK, JC;LIEF, JH
在杂合四膜虫的营养无性繁殖过程中，大核无丝分裂，产生表达其中一个等位基因的克隆谱系，但不能同时表达两个等位基因。因为这样的表型分类已经被描述在每个被研究的座位上，它的机制对大核的发育和结构具有重要的意义。研究分类的主要工具是R(F)，即亚克隆稳定表达单个等位基因的比率，以及产量比率，即分类类别的比率。因为R(F)与分类单位的数量有关，所以所有基因座的R(F)恒定意味着所有基因都保持在相同的拷贝数。产出比反映了分类单位的投入比，1：1的产出比意味着在大核发育结束时等位基因的数量相等。因为不同的结果会显示不同的大核结构，所以准确测量这些参数是至关重要的。虽然公布的R(F)值对于所有测量的基因座都是相似的，但还没有一种普遍接受的表示和分析形式。这里我们考察R(F)的实验测定。首先，我们使用计算机模拟来描述分类过程中固有的可变性如何影响R(F)的实验测定。其次，我们描述了一种简单的绘制分类数据的方法，该方法允许统一计算R(F)，并描述了在可能仅对隐性等位基因评分的情况下如何准确地测量R(F)。使用这种方法为所有已发表的数据产生真正可比的R(F)S，我们发现R(F)S的大部分(如果不是全部)基因座分类与已断言的大约45个分类单位一致。
During vegetative, asexual reproduction in heterozygous Tetrahymena thermophila, the macronucleus divides amitotically to produce clonal lineages that express either one or the other allele but not both. Because such phenotypic assortment has been described for every locus studied, its mechanism has important implications concerning the development and structure of the macronucleus. The primary tools to study assortment are R(f), the rate at which subclones come to express a single allele stably, and the output ratio, the ratio of assortee classes. Because R(f) is related to the number of assorting units, a constant R(f) for all loci suggests that all genes are maintained at the same copy number. Output ratios reflect the input ratio of assorting units, with a 1:1 output ratio implying equal numbers of alleles at the end of macronuclear development. Because different outcomes would suggest a different macronuclear structure, it is crucial that these parameters be accurately measured. Although published R(f) values are similar for all loci measured, there has been no commonly accepted form of presentation and analysis. Here we examine the experimental determination of R(f). First, we use computer simulation to describe how the variability inherent in the assortment process affects experimental determination of R(f). Second, we describe a simple method of plotting assortment data that permits the uniform calculation of R(f), and we describe how to measure R(f) accurately in instances when it is possible to score only the recessive allele. Using this method to produce truly comparable R(f)s for all published data, we find that most, if not all, loci assort at R(f)s consistent with approximately 45 assorting units, as has been asserted.