Ayala F J
Proc Natl Acad Sci U S A. 1982 Jan;79(2):550-4. doi: 10.1073/pnas.79.2.550.
Electrophoretic studies have shown that the average frequency of heterozygous loci per individual is about 12% in Drosophila and other invertebrates and about 6% in vertebrates. It is estimated that only about two-thirds of all amino acid substitutions change net electric charge; hence, a large fraction of all genetic variation may be undetected by electrophoresis. Peptide mapping of 11 independent alleles coding for alcohol dehydrogenase in Drosophila melanogaster has uncovered one cryptic variant; thus, the frequency of electrophoretically cryptic variation is apparently low, about 9% in this sample. Nevertheless, with a simple model it is shown that this degree of cryptic variation, if it is typical of other loci, would substantially change our current estimates of genetic variation: the average heterozygosity would increase from about 12% to about 25% for invertebrates and from about 6% to 21% for vertebrates. A variety of techniques--including sequential electrophoresis and heat or urea denaturation--have been used by various investigators to detect electrophoretically cryptic variation. These techniques appear to be less effective than peptide mapping for detecting cryptic variation, but, like peptide mapping, they suggest that standard electrophoresis may detect most of the protein variation present in natural populations. The charge-state model of protein variation proposes that the "alleles" detected by electrophoresis are extremely diverse classes consisting of many electrophoretically cryptic alleles. The alcohol dehydrogenase peptide-mapping results are inconsistent with the charge-state model.
电泳研究表明，果蝇和其他无脊椎动物中，每个个体杂合基因座的平均频率约为12%，脊椎动物中约为6%。据估计，所有氨基酸替换中只有约三分之二会改变净电荷；因此，电泳可能检测不到很大一部分遗传变异。对果蝇中编码乙醇脱氢酶的11个独立等位基因进行肽图分析，发现了一个隐蔽变异体；因此，电泳隐蔽变异的频率显然较低，在这个样本中约为9%。然而，通过一个简单的模型可以看出，如果这种程度的隐蔽变异在其他基因座中具有代表性，将会显著改变我们目前对遗传变异的估计：无脊椎动物的平均杂合度将从约12%增加到约25%，脊椎动物将从约6%增加到21%。不同的研究者使用了多种技术——包括连续电泳以及加热或尿素变性——来检测电泳隐蔽变异。这些技术在检测隐蔽变异方面似乎不如肽图分析有效，但与肽图分析一样，它们表明标准电泳可能检测到自然种群中存在的大部分蛋白质变异。蛋白质变异的电荷状态模型提出，电泳检测到的“等位基因”是由许多电泳隐蔽等位基因组成的极其多样的类别。乙醇脱氢酶肽图分析的结果与电荷状态模型不一致。
