Stump A D, Pombi M, Goeddel L, Ribeiro J M C, Wilder J A, della Torre A, Besansky N J
Center for Global Health and Infectious Diseases, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA.
Insect Mol Biol. 2007 Dec;16(6):703-9. doi: 10.1111/j.1365-2583.2007.00764.x.
In the malaria vector Anopheles gambiae, alternative arrangements of chromosome 2 (2La and 2L+(a)) vary in relative frequency along clines of aridity, suggesting the action of natural selection on targets within the inversion. Our long term goal of detecting such targets depends in part on the level of genetic exchange between arrangements. Accordingly, we estimated recombination rates on 2L from the backcross progeny of 2La/+(a) heterokaryotypes and as a control, from 2L+(a) homokaryotypes. In homokaryotypes, the recombination rate was uniform at ~2.0 centimorgans per megabase (cM/Mb). In heterokaryotypes, recombination within the rearranged region was reduced to < 0.5 cM/Mb, with slightly higher but nevertheless reduced levels (< 1.0 cM/Mb) flanking the rearrangement. Yet, gene exchange was recorded between nearly all markers, including those very near the distal inversion breakpoint. These results suggest that reduced recombination is a necessary but not sufficient mechanism for genetic isolation between alternative arrangements, and that the targets of natural selection can be identified against the different chromosomal backgrounds.
在疟疾媒介冈比亚按蚊中，2号染色体的不同排列形式（2La和2L+(a)）沿着干旱梯度的相对频率有所不同，这表明自然选择作用于倒位区域内的靶点。我们检测此类靶点的长期目标部分取决于排列形式之间的基因交换水平。因此，我们从2La/+(a)异核型的回交后代中估计了2L上的重组率，并作为对照，从2L+(a)同核型中进行了估计。在同核型中，重组率在每兆碱基约2.0厘摩（cM/Mb）处保持一致。在异核型中，重排区域内的重组率降至<0.5 cM/Mb，重排侧翼区域的重组率略高但仍有所降低（<1.0 cM/Mb）。然而，几乎在所有标记之间都记录到了基因交换，包括那些非常靠近远端倒位断点的标记。这些结果表明，重组减少是不同排列形式之间进行遗传隔离的必要但不充分机制，并且可以针对不同的染色体背景识别自然选择的靶点。
