The benefits of sexual reproduction that outweigh its costs have long puzzled biologists. Increased genetic diversity generated by new allelic combinations, as enhanced by recombination during meiosis, is considered a primary benefit of sex. Sex-determining systems have evolved independently on numerous occasions. One of the most familiar is the use of sex chromosomes in vertebrates. Other eukaryotic groups also use sex chromosomes or smaller sex-determining regions within their chromosomes, such as the mating type loci in the fungi. In these organisms, sexual reproduction and its associated meiotic recombination are controlled by regions of the genome that are themselves blocked in recombination. Non-recombining DNA that is essential for recombination presents a paradox. One hypothesis is that sex-determination requires or leads to highly diverse alleles, establishing this block in recombination. A second hypothesis to account for the common occurrence of these types of sex-determining systems is that they combine mechanisms for recombination suppression and reproductive isolation, thereby promoting the evolution of new species. The fungal kingdom represents the ideal eukaryotic lineage to elucidate the functions of non-recombining regions in sex-determination and speciation.

有性生殖的好处超过其成本一直困扰着生物学家。新的等位基因组合产生的遗传多样性增加，减数分裂期间的重组增强，被认为是性的主要好处。性别决定系统曾多次独立进化。最熟悉的一种是在脊椎动物中使用性染色体。其他真核生物群也使用性染色体或染色体内较小的性别决定区域，例如真菌中的交配型基因座。在这些生物体中，有性生殖及其相关的减数分裂重组受基因组区域控制，这些区域本身在重组中被阻止。对重组至关重要的非重组 DNA 呈现出一个悖论。一种假设是性别决定需要或导致高度多样化的等位基因，从而在重组中建立了这一块。解释这些类型的性别决定系统普遍发生的第二个假设是，它们结合了重组抑制和生殖隔离机制，从而促进了新物种的进化。真菌界代表了理想的真核谱系，以阐明非重组区域在性别决定和物种形成中的功能。