Genetic instability in the mating type system of Tetrahymena pigmentosa.
Genetic instability in the mating type system of Tetrahymena pigmentosa.
复制标题
色素四膜虫交配型系统的遗传不稳定性。
DOI：
10.1093/genetics/117.3.437
复制
发表时间：
1987
期刊：
影响因子：
3.3
通讯作者：
E. Orias
中科院分区：
文献类型：
--
作者：
E. M. Simon;E. Orias
四膜虫的自交克隆显示了一些有趣的遗传特征，并提供了一些深入了解交配型（mt）的决定机制。它们与嗜热四膜虫的差异显著。它们在杂交中非随机分布。它们的稳定率是高度可变的，但大多数都远低于T。嗜热菌从几乎所有自交系衍生的许多亚克隆在培养中保持稳定的mts数年。然而，一些亚克隆表现出持续自交，计算完成后很长一段时间的等位基因分配杂合基因座。这种现象沿着在杂合子中显性mt的永久保持，表明表型分类与mt表达无关。在杂交中，许多自交者在将等位基因传递给配子时表现出数量和质量上的畸变;这些畸变背后的一些微核变化发生在营养生长期间。有性后代中显性等位基因的不正常出现是罕见的，而大多数隐性表型的不正常出现则更为常见。各种模型来解释MT决定在这个物种被认为是。可能解释该系统的令人不安的现象的一个因素是由一个活跃的mat表达位点组成，在其他位点上具有对不同显性等位基因特异的“盒”，并且能够转座到表达位点。
Selfing clones of Tetrahymena pigmentosa show several interesting genetic features, and provide some insight into the mechanisms of mating type (mt) determination. They differ significantly from those of Tetrahymena thermophila. They are distributed nonrandomly in crosses. Their rates of stabilization are highly variable, but most are much lower than those reported for T. thermophila. A number of subclones derived from nearly all the selfers have maintained stable mts in culture for several years. However, some subclones manifest persistent selfing, long after the calculated completion of allelic assortment for heterozygous loci. This phenomenon along with the perpetual maintenance of dominant mts in heterozygotes shows that phenotypic assortment is not involved in mt expression. In crosses, many selfers exhibit quantitative and qualitative aberrations in the transmission of alleles to the gametes; some of the micronuclear changes underlying these aberrations occur during vegetative growth. There are rare illegitimate appearances of dominant alleles in sexual progeny, and more common illegitimate appearances of the most recessive phenotype.--Various models to explain mt determination in this species are considered. One which might account for the troubling phenomena of the system consists of an active mat expression site, with "cassettes" at other sites specific for the different dominant alleles and capable of transposition to the expression site.