Stern H, Westergaard M, Von Wettstein D
Proc Natl Acad Sci U S A. 1975 Mar;72(3):961-5. doi: 10.1073/pnas.72.3.961.
We are proposing a "Preselection Hypothesis" to account for the regulation of crossing-over in eukaryotic organisms. The hypothesis characterized meiosis in terms of three major physiological stages: (1) a presynaptic stage when pairs of homologous DNA stretches are selected so as to become trapped within the synaptinemal complex during synapsis, (2) an alignment of homologous chromosomes and stabilization of paired bivalents via the synaptinemal complex, and (3) a scission and rejoining of DNA stretches leading to the formation of chiasmata and crossovers. The hypothesis centers on the first stage and is based on evidence for the occurrence of significant cytological and biochemical changes prior to synapsis. The major feature of the hypothesis is that crossing-over occurs only in trapped DNA stretches. Thus, potential crossing-over sites, though not crossing-over itself, are determined well before chromosomes pair. Since, to a large degree, crossovers are distributed randomly along the length of each chromosome, the preselection process must result in a random assortment of trapped DNA stretches, the assortment differing from one meiocyte to another.
我们提出了一个“预选假说”来解释真核生物中交叉互换的调控机制。该假说从三个主要生理阶段描述减数分裂：（1）突触前阶段，在此阶段，同源DNA片段对被选择，以便在联会期间被困在联会复合体中；（2）同源染色体的排列以及通过联会复合体使配对的二价体稳定；（3）DNA片段的断裂和重新连接，导致交叉点和交叉互换的形成。该假说以第一阶段为核心，并且基于突触形成之前发生显著细胞学和生化变化的证据。该假说的主要特征是交叉互换仅发生在被困的DNA片段中。因此，潜在的交叉互换位点，尽管不是交叉互换本身，在染色体配对之前就已确定。由于在很大程度上，交叉点沿着每条染色体的长度随机分布，预选过程必然导致被困DNA片段的随机组合，这种组合在不同的减数分裂细胞之间存在差异。
