Singh B N, Singh A K
Department of Zoology, Banaras Hindu University, India.
Hereditas. 1990;112(3):203-8. doi: 10.1111/j.1601-5223.1990.tb00058.x.
Two inversions in the opposite arms of the third chromosome are common in natural populations of Drosophila ananassae. When the strains are taken to laboratory, these inversions have been found to persist for several generations. Four natural populations were sampled and the data on the combinations between 3L and 3R karyotypes were obtained. For all the four populations, laboratory stocks (mass culture and isofemale lines) were established and maintained in food bottles by transferring fifty flies in each generation. After ten generations, chromosomes of all stocks were sampled. The results show that the two linked inversions are associated randomly in natural populations and in laboratory stocks established from mass culture. On the other hand, the same two inversions show non-random association (linkage disequilibrium) in several isofemale lines. The random association between inversions in natural and mass culture laboratory populations as contrasted to laboratory populations established from single females suggest that random drift is the cause of non-random association in isofemale lines. The tight linkage between the two inversions as evidenced by the results of recombination studies reported earlier, supports the notion that linkage disequilibrium is caused by drift.
在拟果蝇的自然种群中，第三号染色体相对臂上的两种倒位现象很常见。当这些品系被带到实验室时，发现这些倒位会持续几代。对四个自然种群进行了采样，并获得了3L和3R核型之间组合的数据。对于所有这四个种群，建立了实验室品系（大规模培养和单雌系），并通过每代转移五十只果蝇在食物瓶中进行维持。十代之后，对所有品系的染色体进行了采样。结果表明，这两种连锁倒位在自然种群以及从大规模培养建立的实验室品系中随机关联。另一方面，在几个单雌系中，同样的两种倒位表现出非随机关联（连锁不平衡）。自然种群和大规模培养实验室种群中倒位之间的随机关联，与从单雌建立的实验室种群形成对比，这表明随机漂变是单雌系中非随机关联的原因。如先前报道的重组研究结果所证明的，这两种倒位之间的紧密连锁支持了连锁不平衡是由漂变引起的这一观点。
