Curtsinger James W
Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, USA.
J Gerontol A Biol Sci Med Sci. 2002 Dec;57(12):B409-14. doi: 10.1093/gerona/57.12.b409.
Most of the quantitative trait loci (QTLs) that have been found to influence life span in Drosophila and Mus organisms are reported to have genetic effects limited to one sex. Here I study the statistical properties of sex-limited QTLs by randomly sampling data from an exceptionally large Drosophila experiment, and then asking how sample size influences outcomes. The sampling study suggests that, for the particular data analyzed here, even moderately large experiments, of the order of 10(4) individuals, can have a high probability of detecting sex-limited effects when they are not actually present. If a particular QTL is present in both sexes, and if the probability of detecting it in each sex is moderately high, say 80%, then there is a 32% chance of erroneously concluding that there is sex specificity. A comparison of interval mapping and composite interval mapping methods of data analysis suggests that the latter can inflate the appearance of sex specificity and sexual antagonism, depending on the choice of number of background covariates in the analysis. Conclusive evidence for sex-limited QTLs will require demonstration that results are robust to methods of statistical analysis, and experimental replication.
据报道，在果蝇和小鼠中发现的大多数影响寿命的数量性状基因座（QTL）的遗传效应仅限于一种性别。在这里，我通过从一个特别大的果蝇实验中随机抽样数据来研究性别受限QTL的统计特性，然后探讨样本量如何影响结果。抽样研究表明，对于这里分析的特定数据，即使是中等规模的实验，大约10^4个个体，当实际上不存在性别受限效应时，也有很高的概率检测到这种效应。如果某个特定的QTL在两性中都存在，并且在每种性别中检测到它的概率适中较高，比如80%，那么错误地得出存在性别特异性的结论的概率为32%。对数据分析的区间映射和复合区间映射方法的比较表明，根据分析中背景协变量数量的选择，后者可能会夸大性别特异性和性拮抗的表象。性别受限QTL的确凿证据将需要证明结果对统计分析方法具有稳健性，并且需要实验重复验证。
