Centers for Disease Control and Prevention, Division of Vector-Borne Diseases, Fort Collins, CO, USA.
Ticks Tick Borne Dis. 2013 Feb;4(1-2):63-71. doi: 10.1016/j.ttbdis.2012.07.005. Epub 2012 Dec 7.
Single-nucleotide polymorphisms (SNPs) are the most widespread type of sequence variation in genomes. SNP density and distribution varies among different organisms and genes. Here, we report the first estimates of SNP distribution and density in the genome of the blacklegged tick (Ixodes scapularis), an important vector of the pathogens causing Lyme disease, human granulocytic anaplasmosis and human babesiosis in North America. We sampled 10 individuals from each of 4 collections from New Jersey, Virginia, Georgia, and Mississippi and analyzed the sequences of 9 nuclear genes and the mitochondrial 16S gene. SNPs are extremely abundant (one SNP per every 14 bases). This is the second highest density so far reported in any eukaryotic organism. Population genetic analyses based either on haplotype frequencies or the 372 SNPs in these 9 genes showed that the 40 ticks formed 3 genetic groups. In agreement with earlier population genetic studies, northern ticks from New Jersey and Virginia formed a homogeneous group with low genetic diversity, whereas southern ticks from Georgia and Mississippi consisted of 2 separate groups, each with high genetic diversity.
单核苷酸多态性（SNPs）是基因组中最普遍的序列变异类型。SNP 的密度和分布在不同的生物体和基因之间有所不同。在这里，我们报告了黑腿蜱（Ixodes scapularis）基因组中 SNP 分布和密度的首次估计，黑腿蜱是北美的莱姆病、人类粒细胞无形体病和人类巴贝斯虫病病原体的重要载体。我们从新泽西州、弗吉尼亚州、佐治亚州和密西西比州的 4 个采集点各抽取了 10 个个体，并分析了 9 个核基因和线粒体 16S 基因的序列。SNP 极为丰富（每 14 个碱基就有一个 SNP）。这是迄今为止在任何真核生物中报告的第二高密度。基于单倍型频率或这 9 个基因中的 372 个 SNP 的群体遗传分析表明，这 40 只蜱形成了 3 个遗传群体。与早期的群体遗传研究一致，来自新泽西州和弗吉尼亚州的北部蜱形成了一个具有低遗传多样性的同质群体，而来自佐治亚州和密西西比州的南部蜱则由 2 个具有高遗传多样性的独立群体组成。
