Biémont C
Laboratoire de Biométrie, Génétique, Biologie des populations, URA C.N.R.S. 243, Université Lyon 1, Villeurbanne, France.
J Mol Evol. 1994 Nov;39(5):466-72. doi: 10.1007/BF00173415.
Six highly inbred lines of Drosophila melanogaster extracted from an M' strain (in the P/M system of hybrid dysgenesis) were studied for the evolution of the number and chromosomal location of complete and defective P elements through generations 52-200. These lines possessed full-sized P elements but differed in their cytotype (M or P). Three lines with P cytotype and full-sized P elements at site 1A had a constant P copy number over generations with low rates of insertion and excision. Three lines with M cytotype and at least one full-sized P element accumulated P copies over the generations and reached a plateau near generation 196, at which rates of transposition and excision were equal to 1.2 x 10(-3) to 3 x 10(-3) events per element per generation. At that time these three lines still presented an M cytotype, produced transposase, and were able to regulate P copy number. The similarity at equilibrium between insertion and excision rates was exactly what was expected from theoretical models for a self-regulated element. The large number of generations necessary to attain the equilibrium in copy number indicates, however, that caution may be de rigueur when testing theoretical models of copy-number containment based on transposition and excision-rate comparison.
对从一个M'品系（在杂种不育的P/M系统中）提取的六个高度近交的黑腹果蝇品系进行了研究，观察完整和缺陷型P元件在第52代至200代中的数量及染色体定位的演变。这些品系拥有全长P元件，但细胞型（M或P）不同。三个具有P细胞型且在1A位点有全长P元件的品系在几代中P拷贝数恒定，插入和切除率较低。三个具有M细胞型且至少有一个全长P元件的品系在几代中积累了P拷贝，并在第196代附近达到平稳状态，此时转座和切除率等于每元件每代1.2×10⁻³至3×10⁻³次事件。那时这三个品系仍呈现M细胞型，产生转座酶，并能够调节P拷贝数。插入和切除率在平衡时的相似性正是自调节元件理论模型所预期的。然而，达到拷贝数平衡所需的大量代数表明，在基于转座和切除率比较来测试拷贝数控制的理论模型时，可能需要格外谨慎。
