斑点叉尾鮰趋化因子基因SCYA113内含子1的多态性分析

运用变性聚丙烯酰胺凝胶电泳和PCR产物测序技术检测斑点叉尾鮰CC趋化因子基因SCYA113 内含子1的序列长度和多态性。在3个群体的60个个体中，斑点叉尾鮰CC趋化SCYA113 内含子1存在15种单元型和8种长度类型，长度类型分别为A、B、C、D、E、F、G和H型。对这8种序列进行比对分析发现，斑点叉尾鮰SCYA113 内含子1长度为395~443 bp， 8种长度类型中A、G、T、C的平均百分比为30.01%、15.43%、38.37%、16.19%，而且G+C（31.62%）含量明显小于A+T（68.38%）含量，内含子1与外显子1和2的连接处存在真核基因中mRNA剪接的识别信号GT/AG；引起长度变化的主要原因是短串联重复序列（微卫星序列）TTC和TTA引起的；除了微卫星序列以外，共检测到6个突变位点，其中3个转换位点为118（C→T），209（G→A），250（T→C），3个颠换位点为266（T→A），289（G→T），387（G→C），核苷酸多样性指数(π)为0.004，平均核苷酸差异(K)为1.576；在变异水平上，3个群体表现出一定的遗传差异，84群体中检测到8种长度类型和14种基因型，97群体中检测到8种长度类型和10种基因型，04群体中6种长度类型和10种基因型（缺少A、B等位基因）。从3个群体60个个体拥有22种频率较低(0.017~0.150)的基因型可以看出，斑点叉尾鮰的遗传基因资源较为丰富。

Polymorphism analysis of intron 1 of chemokine SCYA113 in channel catfish (Ictalurus Punctatus)

Size and nucleotide polymorphisms of intron 1 of chemokine gene SCYA113 were studied in 60 individuals from 3 populations of channel catfish (Ictalurus Punctatus) with DPAGE and DNA sequencing. Results showed that there were 15 haplotypes and 8 length variants (from A to H), ranging from 395 to 443 bp. Sequence analysis of the 8 length variants showed the average composition of nucleotides (A, G, T and C) were 30.01%, 15.43%, 38.37% and 16.19%, respectively, and the GC content (31.62%) was much lower than that of AT content (68.38%). The GT/AG domain was found in exon-intron junctions,which was the 5′ and 3′ splice donor and acceptor sites in higher eukaryotic gene introns. Length variation was mainly due to the variable number of microsatellite TTC and TTA repeats. There were only 6 substitution sites excluding microsatellites: 3 transversions at 266 (T→A), 289 (G→T), 387 (G→C) and 3 transitions at 118 (C→T), 209 (G→A) and 250 (T→C), respectively. And the nucleotide diversity (π) was only 0.004, average number of nucleotide differences (K) was 1.576. The three populations have displayed the genetic diversity. In the P1984 population, eight length types and fourteen genotypes were observed. Eight length types and ten genotypes presented in the P1997 population. In the P2004 population, there were six length types and ten genotypes, and no allele A and B were found. Twenty-two genotypes are found from 60 individuals. All the genotypes are emerging at a lower frequencies (from 0.017 to 0.150), indicating the genetic resources is abundant.