Shaw F H, Promislow D E, Tatar M, Hughes K A, Geyer C J
Department of Ecology, Evolution, and Behavior, University of Minnesota, Saint Paul, Minnesota 55108, USA.
Genetics. 1999 Jun;152(2):553-66. doi: 10.1093/genetics/152.2.553.
Standard models for senescence predict an increase in the additive genetic variance for log mortality rate late in the life cycle. Variance component analysis of age-specific mortality rates of related cohorts is problematic. The actual mortality rates are not observable and can be estimated only crudely at early ages when few individuals are dying and at late ages when most are dead. Therefore, standard quantitative genetic analysis techniques cannot be applied with confidence. We present a novel and rigorous analysis that treats the mortality rates as missing data following two different parametric senescence models. Two recent studies of Drosophila melanogaster, the original analyses of which reached different conclusions, are reanalyzed here. The two-parameter Gompertz model assumes that mortality rates increase exponentially with age. A related but more complex three-parameter logistic model allows for subsequent leveling off in mortality rates at late ages. We find that while additive variance for mortality rates increases for late ages under the Gompertz model, it declines under the logistic model. The results from the two studies are similar, with differences attributable to differences between the experiments.
衰老的标准模型预测，在生命周期后期，对数死亡率的加性遗传方差会增加。对相关队列特定年龄死亡率进行方差成分分析存在问题。实际死亡率不可观测，在早期很少有人死亡以及晚期大多数人已死亡时，只能进行粗略估计。因此，无法自信地应用标准定量遗传分析技术。我们提出了一种新颖且严谨的分析方法，该方法在遵循两种不同参数衰老模型的情况下，将死亡率视为缺失数据。这里重新分析了两项最近关于黑腹果蝇的研究，其最初分析得出了不同结论。双参数冈珀茨模型假设死亡率随年龄呈指数增长。一个相关但更复杂的三参数逻辑模型允许死亡率在后期趋于平稳。我们发现，虽然在冈珀茨模型下，后期死亡率的加性方差增加，但在逻辑模型下它会下降。两项研究的结果相似，差异归因于实验之间的差异。
