Variation in toll-like receptor 21 within and among killifish (fundulus heteroclitus) populations from southeastern Massachusetts and northern Maine
Sanborn, Jeffrey S. Jr.
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Through polymorphisms occurring within immune system genes, the immune system is able to retain greater diversity and better co-evolve alongside pathogen populations. Adaptive molecular variation clearly indicates that single nucleotide polymorphisms (SNPs) are not stochastically distributed and that those adaptive in nature can be linked to diverse ecological stressors and natural selection. The goal of this study was threefold; (1) To verify the annotated gene model for TLR21, (2) to verify an INDEL polymorphism in the 5’ putative regulatory region of TLR21 that was previously described by Soucier, and (3) to study levels of variation in TLR21 within and among Northern Maine and Southeastern Massachusetts populations of Fundulus. We found that the proposed modified model for TLR21 was correct and now describes the full gene. Furthermore, I verified the 6bp insertion polymorphism previously described by Soucier. In addition I found substantial levels of genetic diversity within and among populations in Maine and Massachusetts with high levels of divergence at some single nucleotide polymorphic sites. No statistically significant differences in the variation of SNPs was detected between contaminated and non-contaminated sites or between Maine and Massachusetts’s populations. Though I was not able to demonstrate a clear association between any single SNP and environmental differences among populations, several SNP positions demonstrated evidence suggestive of natural selection.
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