染色体重复与进化.doc

Chromosomal?duplication?is a transient evolutionary solution to stress. Yona AH,?Manor YS,?Herbst RH,?Romano GH,?Mitchell A,?Kupiec M,?Pilpel Y,?Dahan O. /pubmedAbstract Aneuploidy, an abnormal number of chromosomes, is a widespread phenomenon found in unicellulars such as yeast, as well as in plants and in mammalians, especially in cancer. Aneuploidy is a?genome-scale aberration that imposes a severe burden on the cell, yet under stressful conditions specific aneuploidies confer a selective advantage. This dual nature of aneuploidy raises the question of whether it can serve as a stable and sustainable evolutionary adaptation. To clarify this, we conducted a set of laboratory?evolution?experiments in yeast and followed the long-term dynamics of aneuploidy under diverse conditions. Here we show that chromosomal duplications are first acquired as a crude solution to stress, yet only as transient solutions that are eliminated and replaced by more efficient solutions obtained at the individual gene level. These transient dynamics of aneuploidy were repeatedly observed in our laboratory?evolution?experiments; chromosomal duplications gained under stress were eliminated not only when the stress was relieved, but even if it persisted. Furthermore, when stress was applied gradually rather than abruptly, alternative solutions appear to have emerged, but not aneuploidy. Our findings indicate that chromosomal?duplication?is a first evolutionary line of defense, that retains survivability under strong and abrupt selective pressures, yet it merely serves as a quick fix, whereas more refined and sustainable solutions take over. Thus, in the perspective of?genome?evolution?trajectory, aneuploidy is a useful yet short-lived intermediate that facilitates further adaptation. Keywords:?evolutionary dynamics, environmental stress, heat tolerance, pH tolerance 染色体重复与进化 11应用生物教育A班 杨万坤 114120238 摘要：随着染色体技术的不断发展，对染色体结构的研究不断发掘，这些研究结果被广泛地应用到遗传育种、遗传病理研究工作中，特别是对生物的染色体结构变