Many species are able to hybridize, but the sterility of these hybrids effectively prevents gene flow between the species, reproductively isolating them and allowing them to evolve independently. Yeast hybrids formed by Saccharomyces cerevisiae and Saccharomyces paradoxus parents are viable and able to grow by mitosis, but they are sexually sterile because most of the gametes they make by meiosis are inviable. The genomes of these two species are so diverged that they cannot recombine properly during meiosis, so they fail to segregate efficiently. Thus most hybrid gametes are inviable because they lack essential chromosomes. Recent work shows that chromosome mis-segregation explains nearly all observed hybrid sterility-genetic incompatibilities have only a small sterilising effect, and there are no significant sterilising incompatibilities in chromosome arrangement or number between the species. It is interesting that chromosomes from these species have diverged so much in sequence without changing in configuration, even though large chromosomal changes occur quite frequently, and sometimes beneficially, in evolving yeast populations.

中文翻译：

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酵母悖论：不同物种的染色体不相容是因为抗重组，而不是因为数目或排列上的差异。

许多物种能够杂交，但是这些杂交物种的不育性有效地阻止了物种之间的基因流动，繁殖地分离它们并使它们独立进化。由酿酒酵母和悖酒酵母父母形成的酵母杂种是可行的，并能够通过有丝分裂生长，但是它们是不育性的，因为它们通过减数分裂产生的大多数配子是不能繁殖的。这两个物种的基因组是如此分散，以至于它们在减数分裂过程中无法正确重组，因此它们无法有效地分离。因此，大多数杂配子由于缺乏必需的染色体而无法繁殖。最近的研究表明，染色体的错误分离解释了几乎所有观察到的杂种不育遗传不相容性仅具有很小的灭菌效果，并且在物种之间的染色体排列或数目上没有明显的灭菌不相容性。有趣的是，即使在不断发展的酵母菌群体中发生较大的染色体变化（有时是有益的），来自这些物种的染色体却在序列上发生了如此大的变化而没有改变构型。