PNAS：劣质基因可能导致突变熔毁


			

		
	

	
关键词：突变,劣质基因,灭绝
多伦多大学的进化生物学家已经发现，劣质基因个体可能产生更劣质染色体的后代，可能导致世代中某些物种灭绝。
此研究发表在PNAS上，指出：相对于高质量基因个体来说，遗传缺陷生物可能经历DNA突变量增加。该研究以果蝇为研究对象，因为果蝇的简单系统是更复杂系统中生物学诸多方面的模仿，因此，此研究发现可能对人类有所启发。
在此研究中，研究人员检测了黑腹果蝇的基因突变累积，这些基因排列在3个主要染色体上。为了操控基因质量，果蝇三号染色体被引入有害突变，以便观察这些突变的存在如何影响2号染色体在46代内的适应性。结果是，劣质基因提高了突变率。
尽管还不清楚这种现象所含的机制，但这可能与受影响个体低DNA修复能力或高DNA易损性有关。对于遗传学研究，果蝇尤其有用，因为可用成千上万果蝇筛查成千上万的基因，饲养费用低，繁殖快，只在几个月内就有几代果蝇可供研究。值得注意的是，在遗传学压力或环境压力的情况下，升高的突变率也可能加速适应新环境。（生物谷bioon.com）





doi:10.1073/pnas.1118918109
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Evidence for elevated mutation rates in low-quality genotypes
N. P. Sharp, A. F. Agrawal
The deleterious mutation rate plays a key role in a number of important topics in biology, from mating system evolution to human health. Despite this broad significance, the nature and causes of variation in mutation rate are poorly understood, especially in multicellular organisms. We test whether genetic quality, the presence or absence of deleterious alleles, affects the mutation rate inDrosophila melanogaster by using a modified mutation accumulation approach. We find evidence that genotypes constructed to carry deleterious "treatment" alleles on one chromosome during mutation accumulation experience an elevated mutation rate on a different chromosome. Further, this elevation is correlated with the effect of the treatment alleles on phenotypic condition, measured as body mass. Treatment alleles that reduce mass by 10% cause a doubling in the rate of mutational decline. Our results show that mutation rates are sensitive to genetic stress, such that individuals with low-quality genotypes will produce offspring of even lower genetic quality, in a mutational positive feedback loop. This type of variation in mutation rate is expected to alter a variety of predictions based on mutation load theory and accelerate adaptation to new environments. Positive mutational feedback could affect human health by increasing the rate of germline mutation, and possibly somatic mutation, in individuals of poor health because of genetic or environmental stress.