Date of Award

2008

Document Type

Restricted Thesis

Terms of Use

© 2008 Lenore Pipes. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts

Department

Biology Department

Abstract

Over 70 years ago, it was reported that humans vary in taste sensitivity to the bitter compound phenylthiocarbamide (PTC). The inability to taste PTC is a classic phenotype that has long been assumed to be attributed to the recessive allele in a one-locus, two-allele system. PTC perception has been recognized to vary in all human populations to date. This variability is mainly controlled by the segregation of two common alleles at the TAS2R38 locus on chromosome 7, which encode receptor variants with different ligand affinities. The human TAS2R38 gene has been shown to occur in six haplotypic forms, although only two of these, PAV and AVI, respectively, are associated with the major taster and non-taster phenotypes that have been observed in every population tested to date. This pattern of variation suggests that natural selection may have favored TAS2R38 alleles that are responsive to toxic, bitter phytochemical compounds naturally found in the environment. However, there is relatively little information about tasting gene variation in northern Asian populations. Therefore, to better understand patterns of tasting abilities in this region, we analyzed variation at the TAS2R38 locus in a sample of 253 individuals from indigenous Northern Altaian populations and 187 individuals from Southern Altaian populations in south-central Siberia. We screened the samples for two informative SNPs within the TAS2R38 gene using TaqMan assays that generate taster and non-taster phenotypes. Our data revealed a mixture of haplotypes related to differential tasting ability, as well as previously unrecognized haplotypes in these indigenous groups. We discuss the implications of these data for the genetic relationships of native Altaian populations with other modern human groups, and the possible effects of geographic isolation and adaptation on the patterns of allelic variation seen in south-central Siberia.

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