Dutcher S K
Basic Life Sci. 1986;40:303-25. doi: 10.1007/978-1-4684-5251-8_24.
A unique linkage group has been identified in Chlamydomonas. To date, all mutations that have been mapped to linkage group XIX affect flagellar and basal body functions. Linkage group XIX shows several other striking genetic properties. First, the genetic map of this linkage group is circular. Genetic circularity can be achieved because the chromosome is a physically circular molecule or because of constraints on the types of recombination events that occur. A linear molecule that shows complete chromatid interference cannot be distinguished from a circular molecule. Complete chromatid interference is defined as the property that every chromatid is always involved in an even number of recombination events. If interference is not complete, three factor crosses will distinguish between a circular chromosome and a linear chromosome. Experiments of this type are underway (S.K. Dutcher, work in progress). Second, recombination levels on linkage group XIX are affected by temperature; recombination on 12 other linkage groups in Chlamydomonas is not affected by changes in temperature during any part of the meiotic life cycle (S.K. Dutcher, ms. in prep.). Patterns of interference and recombination on linkage group XIX are also different from other linkage groups. Basal bodies/centrioles are cellular organelles that are precisely replicated and partitioned in cell division. This fidelity distinguishes basal bodies/centrioles from all other cellular organelles, with the exception of the nucleus and the chromosomes. Because of the odd genetics of linkage group XIX and the strict replication and segregation of basal bodies, it is intriguing to speculate on the location of linkage group XIX. There are numerous reports in the literature of nucleic acid being associated with basal bodies. Both RNA and DNA have been reported to be localized to these structures. To date no unique species has been identified. Lwoff has suggested that basal bodies are genetically autonomous, and Sagan has suggested that they could have a symbiotic origin. Could linkage group XIX be located in the basal body and not in the nucleus? No definitive answer is available to this question. The number of chromosomes in the nucleus of Chlamydomonas has not been determined reliably. Linkage group XIX segregates as expected for a nuclear chromosome and appears to contain a region that behaves genetically as a centromere. However, any genetic information that is partitioned at meiosis in a regular manner and is present in a limited number of copies could resemble a nuclear chromosome in its segregational properties.(ABSTRACT TRUNCATED AT 400 WORDS)
在衣藻中已鉴定出一个独特的连锁群。迄今为止，所有已定位到连锁群XIX的突变都影响鞭毛和基体功能。连锁群XIX还表现出其他几个显著的遗传特性。首先，这个连锁群的遗传图谱是环状的。遗传环状性可以通过染色体是物理环状分子来实现，也可以由于发生的重组事件类型受到限制而实现。一个表现出完全染色单体干涉的线性分子无法与环状分子区分开来。完全染色单体干涉被定义为每个染色单体总是参与偶数次重组事件的特性。如果干涉不完全，三因子杂交将区分环状染色体和线性染色体。此类实验正在进行中（S.K. 达彻，工作进行中）。其次，连锁群XIX上的重组水平受温度影响；衣藻中其他12个连锁群上的重组在减数分裂生命周期的任何阶段都不受温度变化的影响（S.K. 达彻，准备中的手稿）。连锁群XIX上的干涉和重组模式也与其他连锁群不同。基体/中心粒是细胞器，在细胞分裂中精确复制并分配。这种保真度使基体/中心粒与所有其他细胞器不同，除了细胞核和染色体。由于连锁群XIX奇特的遗传学以及基体严格的复制和分离，推测连锁群XIX的位置很有趣。文献中有许多关于核酸与基体相关的报道。RNA和DNA都已被报道定位于这些结构。迄今为止，尚未鉴定出独特的物种。勒沃夫提出基体在遗传上是自主的，萨根提出它们可能有共生起源。连锁群XIX会不会位于基体而不是细胞核中呢？这个问题尚无定论。衣藻细胞核中的染色体数量尚未可靠确定。连锁群XIX作为核染色体按预期分离，并且似乎包含一个在遗传行为上类似于着丝粒的区域。然而，任何在减数分裂时以规则方式分配且拷贝数有限的遗传信息，在其分离特性上可能类似于核染色体。（摘要截断于400字）
