Hall T J, Grula J W, Davidson E H, Britten R J
J Mol Evol. 1980 Dec;16(2):95-110. doi: 10.1007/BF01731580.
New methods have been applied to the determination of single copy DNA sequence differences between the sea urchin species Strongylocentrotus purpuratus, S. franciscanus, S. drobachiensis, and Lytechinus pictus. The thermal stability of interspecies DNA duplexes was measured in a solvent (2.4 M tetraethylammonium chloride) that suppresses the effect of base composition on melting temperature. The lengths of duplexes were measured after digestion with S1 nuclease and correction made for the effect of length on thermal stability. The degree of base substitution that has occurred in the single copy DNA during sea urchin evolution is significantly larger than indicated by earlier measurements. We estimate that 19% of the nucleotides of the single copy DNA are different in the genomes of the two sea urchin congeners, S. purpuratus, and S. franciscanus, which apparently diverged only 15 to 20 million years ago.
新方法已应用于测定紫海胆、加州紫海胆、北方球海胆和刺冠海胆这几种海胆物种之间单拷贝DNA序列的差异。种间DNA双链体的热稳定性是在一种抑制碱基组成对解链温度影响的溶剂（2.4 M 四乙基氯化铵）中测量的。用S1核酸酶消化后测量双链体的长度，并对长度对热稳定性的影响进行校正。在海胆进化过程中，单拷贝DNA中发生的碱基替代程度明显大于早期测量结果所显示的。我们估计，在紫海胆和加州紫海胆这两种明显在仅1500万至2000万年前就分化的海胆同属物种的基因组中，单拷贝DNA的19%的核苷酸是不同的。
