Zolan M E
Department of Biology, Indiana University, Bloomington 47405, USA.
Microbiol Rev. 1995 Dec;59(4):686-98. doi: 10.1128/mr.59.4.686-698.1995.
The examination of fungal chromosomes by pulsed-field gel electrophoresis has revealed that length polymorphism is widespread in both sexual and asexual species. This review summarizes characteristics of fungal chromosome-length polymorphism and possible mitotic and meiotic mechanisms of chromosome length change. Most fungal chromosome-length polymorphisms are currently uncharacterized with respect to content and origin. However, it is clear that long tandem repeats, such as tracts of rRNA genes, are frequently variable in length and that other chromosomal rearrangements are suppressed during normal mitotic growth. Dispensable chromosomes and dispensable chromosome regions, which have been well documented for some fungi, also contribute to the variability of the fungal karyotype. For sexual species, meiotic recombination increases the overall karyotypic variability in a population while suppressing genetic translocations. The range of karyotypes observed in fungi indicates that many karyotypic changes may be genetically neutral, at least under some conditions. In addition, new linkage combinations of genes may also be advantageous in allowing adaptation of fungi to new environments.
通过脉冲场凝胶电泳对真菌染色体进行检查发现，长度多态性在有性和无性物种中都很普遍。本综述总结了真菌染色体长度多态性的特征以及染色体长度变化可能的有丝分裂和减数分裂机制。目前，大多数真菌染色体长度多态性在内容和起源方面尚未得到表征。然而，很明显，长串联重复序列，如rRNA基因片段，其长度经常可变，并且在正常有丝分裂生长过程中其他染色体重排受到抑制。在一些真菌中已有充分记录的可有可无染色体和可有可无染色体区域，也导致了真菌核型的变异性。对于有性物种，减数分裂重组增加了群体中总体核型变异性，同时抑制了遗传易位。在真菌中观察到的核型范围表明，许多核型变化可能至少在某些条件下是遗传中性的。此外，基因的新连锁组合在使真菌适应新环境方面也可能具有优势。
