3月26日,，PNAS在線發(fā)表加拿大多倫多大學生態(tài)與進化生物學系研究人員的研究論文,，研究人員發(fā)現擁有低質量基因的個體可能產生遺傳質量更低的后代——至少在果蠅身上是這樣。
Nathaniel Sharp 和Aneil Agrawal通過研究黑腹果蠅（Drosophila melanogaster）評估了遺傳突變如何積累,，這是一種常用于實驗模型的果蠅,。在蠅類身上，基因位于三個主要的染色體上,。為了操縱遺傳質量,，科研人員向這些果蠅的3號染色體引入了有害突變。作者然后觀察了在缺少自然選擇的情況下這些變化如何影響46代后代的2號染色體,。與擁有高質量的3號染色體的果蠅相比,，擁有低質量的3號染色體的果蠅的2號染色體的適應度衰退速度是前者的2到3倍，這提示基因質量不良增加了后代的突變率,。
這項發(fā)現背后的機制尚不明確,，但是作者提出修復DNA損傷的能力可能在后代中被削弱了。此前的研究已經確定了突變在抑郁癥,、癌癥和在人類與其他物種的一系列其他健康問題上起關鍵作用,。作者說,，這項研究提示基因質量不良可能讓這類健康問題復雜化并且導致能夠傷害瀕危種群的災難性突變。（生物谷 bioon.com）
doi:10.1073/pnas.1118918109
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PMID:
Evidence for elevated mutation rates in low-quality genotypes
Nathaniel P. Sharp,，Aneil F. Agrawa
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 in Drosophila 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.
