Germond J E, Walker P, ten Heggeler B, Brown-Luedi M, de Bony E, Wahli W
Nucleic Acids Res. 1984 Nov 26;12(22):8595-609. doi: 10.1093/nar/12.22.8595.
Electron microscopic analysis of heteroduplexes between the most distantly related Xenopus vitellogenin genes (A genes X B genes) has revealed the distribution of homologous regions that have been preferentially conserved after the duplication events that gave rise to the multigene family in Xenopus laevis. DNA sequence analysis was limited to the region downstream of the transcription initiation site of the Xenopus genes A1, B1 and B2 and a comparison with the Xenopus A2 and the major chicken vitellogenin gene is presented. Within the coding regions of the first three exons, nucleotide substitutions resulting in amino acid changes accumulate at a rate similar to that observed in globin genes. This suggests that the duplication event which led to the formation of the A and B ancestral genes in Xenopus laevis occurred about 150 million years ago. Homologous exons of the A1-A2 and B1-B2 gene pairs, which formed about 30 million years ago, show a quite similar sequence divergence. In contrast, A1-A2 homologous introns seem to have evolved much faster than their B1-B2 counterparts.
对非洲爪蟾中亲缘关系最远的卵黄生成素基因（A基因X B基因）之间的异源双链体进行电子显微镜分析，揭示了在导致非洲爪蟾多基因家族产生的复制事件之后优先保守的同源区域的分布。DNA序列分析仅限于非洲爪蟾基因A1、B1和B2转录起始位点下游的区域，并与非洲爪蟾A2基因和鸡的主要卵黄生成素基因进行了比较。在前三个外显子的编码区域内，导致氨基酸变化的核苷酸替换以与在珠蛋白基因中观察到的速率相似的速度积累。这表明导致非洲爪蟾中A和B祖先基因形成的复制事件发生在约1.5亿年前。大约在3000万年前形成的A1 - A2和B1 - B2基因对的同源外显子显示出非常相似的序列分歧。相比之下，A1 - A2同源内含子的进化似乎比它们的B1 - B2对应物快得多。
