Gethmann R C
Department of Biological Science, University of Maryland-Baltimore County Catonsville.
J Hered. 1988 Sep 1;79(5):344-350. doi: 10.1093/oxfordjournals.jhered.a110526.
Achiasmatic meiosis, or meiosis without crossing over, is characteristic of all higher Diptera males (suborder Brachycera). However, several cases of spontaneous crossing over in males have been reported in several different species. An examination of the published data suggests that recombinant chromosomes recovered from heterozygous males are usually the result of spontaneous crossing over in premeiotic cells. Mitotic, or somatic, crossing over probably occurs at a low frequency in all Diptera. When the crossover occurs in a gonial cell line, the recombinant chromosomes can be recovered in the gametes as presumptive meiotic crossovers. In cases where there is a translocation between the Y chromosome and an autosome, the segregation of the chromosomes from the translocation complex can produce aneuploids that phenotypically appear to be crossovers. Chromosome rearrangements and insertion elements, including the male sex-determining factor in Musca domestica and Megaselia scalaris, increase the frequency of exchange. Drosophlia ananassae appears to be an exception to the above. Genetic evidence in D. ananassae suggests that crossing over is a meiotic event and is controlled by a series of suppressors and enhancers.
无交叉减数分裂，即不发生交叉互换的减数分裂，是所有高等双翅目雄性昆虫（短角亚目）的特征。然而，在几个不同物种中都报道了雄性自发交叉互换的案例。对已发表数据的研究表明，从杂合雄性中回收的重组染色体通常是减数分裂前细胞中自发交叉互换的结果。有丝分裂或体细胞交叉互换在所有双翅目中可能以低频率发生。当交叉互换发生在生殖细胞系中时，重组染色体可以作为假定的减数分裂交叉互换在配子中回收。在Y染色体和常染色体之间存在易位的情况下，来自易位复合体的染色体分离可产生表型上看似交叉互换的非整倍体。染色体重排和插入元件，包括家蝇和黑腹果蝇中的雄性性别决定因子，会增加交换频率。果蝇似乎是上述情况的一个例外。果蝇的遗传证据表明，交叉互换是一个减数分裂事件，并受一系列抑制因子和增强因子的控制。
