Sandler L, Szauter P
Genetics. 1978 Dec;90(4):699-712. doi: 10.1093/genetics/90.4.699.
Crossing over was measured on the normally achiasmate fourth chromosome in females homozygous for one of our different recombination-defective meiotic mutants. Under the influence of those meiotic mutants that affect the major chromosomes by altering the spatial distribution of exchanges, meiotic fourth-chromosome recombinants were recovered irrespective of whether or not the meiotic mutant decreases crossing over on the other chromosomes. No crossing over, on the other hand, was detected on chromosome 4 in either wild type or in the presence of a meiotic mutant that decreases the frequency, but does not affect the spatial distribution, of exchange on the major chromosomes. It is concluded from these observations that (a) in wild type there are regional constraints on exchange that can be attenuated or eliminated by the defects caused by recombination-defective meiotic mutants; [b] these very constraints account for the absence of recombination on chromosome 4 in wild type; and [c] despite being normally achiasmate, chromosome 4 responds to recombination-defective meiotic mutants in the same way as do the other chromosomes.
在我们不同的重组缺陷型减数分裂突变体之一的纯合雌性个体中，对通常无交叉的第四条染色体上的交叉进行了测量。在那些通过改变交换的空间分布来影响主要染色体的减数分裂突变体的影响下，无论减数分裂突变体是否降低了其他染色体上的交叉，都能回收减数分裂第四条染色体的重组体。另一方面，在野生型中或在存在降低主要染色体上交换频率但不影响其空间分布的减数分裂突变体的情况下，在第四条染色体上均未检测到交叉。从这些观察结果可以得出以下结论：（a）在野生型中，存在对交换的区域限制，这些限制可以通过重组缺陷型减数分裂突变体引起的缺陷而减弱或消除；（b）正是这些限制导致了野生型中第四条染色体上没有重组；（c）尽管第四条染色体通常无交叉，但它对重组缺陷型减数分裂突变体的反应与其他染色体相同。
