大黄鱼与小黄鱼细胞色素b基因全序列的比较分析

对大黄鱼、小黄鱼线粒体细胞色素b基因进行了PCR扩增及序列测定,得到1140bp的全序列。大黄鱼和小黄鱼的碱基组成相似,前者T、C、A、G含量分别为28.4%、33.0%、23.2%和15.4%,A+T含量为51.6%;后者T、C、A、G含量分别为26.7%、34.1%、23.8%和15.4%,A+T含量为50.5%。大、小黄鱼cytb基因中三联体密码子中碱基的使用频率很相似,第一位较均一,第二位富含T,第三位富含C。大小黄鱼cytb基因存在明显差异,序列相似性仅为88.95%;两序列间具有126个差异位点;碱基转换/颠换率为3.1,碱基替换多发生在密码子第三位;碱基转换中C\T显著高于A\G,表现出转换偏歧。

Comparative analysis of the mitochondrial cytochrome b gene for Pseudosciaena crocea (Richardson) and P. polyactics Bleeker

The complete cytochrome b gene sequences of the large yellow croaker and the small yellow croaker were obtained and analyzed for the nucleotide compositions and the nucleotide pair frequencies. The contents of T、C、A、G、A+T were 28.4%/26.7%、33.0%/34.1%、23.2%/23.8%、15.4%/15.4% 、51.6%/50.5% in the cytb gene sequences of the large/small yellow croakers. Both gene sequences of these two species show similar traits in the nucleotide compositions and the nucleotide pair frequencies. The first codon positions showed no bias to any of the four nucleotides as a whole, while the second and third positions were rich in T and C respectively. 126 nucleotide sites were substituted and sequences similarity was merely 88.95% between these two sequences. The ratio of transitional to transversional substitution was 3.1 with the transitional rate between pyrimidines(C and T) being higher than that between purines(A and G). Most of the base substitutions occurred at the third loci of the codons.