Bitter Taster Detector II
From Genotypes to Phenotpes
A Kit to Determine Your PTC Sensitivity Genotype in one single PCR

  • Ideal for College and Advanced High School Genetic Laboratory Activities
  • Great tool to link individual's genotype to phenotype
  • Hands on CSI-style swab DNA Isolation
  • Simple PCR and gel Electrophoresis allow Allelic Specific Genotyping
  • Correctly assign All Taster Genotypes (TT, Tt, or tt) in one single-tube PCR reaction
  • Class data allow actual testing of the Hardy-Weinberg Equilibrium Theory
  • Great demonstration of personal genetics and inheritance


Introduction

Individuals vary greatly in their sensitivity to the bitter compound Phenylthiocarbamide (PTC). This is one of the best known genetic traits in the human population and historically has been the most popular teaching subject in genetic inheritance. However, the classic PTC paper test falls short of differentiating between homozygous vs heterozygous in the taster alleles. Here we introduce a PCR method to identify an individual’s DNA haplotypes for the PTC receptor gene. Upon gel electrophoresis, the homozygous or heterozygous state of the taster/nontaster alleles can be correctly determined, allowing accurate prediction of one’s PTC taste phenotype. This kit provides an excellent hands-on opportunity for students to correlate their genotypic variations to differences in phenotypes.

Background


Variation in PTC sensitivity was discovered in the 1930s, and it has since been widely used in genetic and population studies. It has enjoyed great attention among geneticists and in class rooms as an informative and easily typed genetic marker. Particularly because variations in PTC sensitivity is regardless of sex, age, and race, and is impossible to predict the phenotypes before testing. Yet when tested, the outcomes can be drastically different even among siblings. For majority of the population, the inheritance appears to follow simple Mendelian rule. Thus it has traditionally been viewed as one of the best human trait for classroom teaching of genetic inheritance.

The PTC Sensitivity Gene-TAS2R38

The gene responsible for PTC sensitivity was identified in 2003, more than 70 years after its original discovery. TAS2R38 encodes a G protein coupled membrane receptor protein. Analysis of SNPs (single nucleotide polymorphisms) along the coding region of TAS2R38 revealed that taster and nontaster alleles differ by just 3 amino acid changes.

Picture 6


Typing PTC Sensitivity by Allele-Specific PCR

We have developed a PCR strategy to simultaneously amplify both the taster and the non-taster alleles in a single-tube PCR reaction. In this method, genomic DNA, isolated from buccal swabs by a column-based DNA isolation procedure, is added to a PCR reaction tube that contains two pairs of primers. During PCR amplification, the taster primer pair amplifies a 300-bp taster gene fragment whereas non-taster primer pair produces a 380-bp band specific to the non-taster allele. In the cases of DNA from heterozygous individuals, both 380-bp and 300-bp fragments will be amplified. PCR products are resolved by gel electrophoresis and presence of DNA bands on gel is indicative of the presence of taster only, non-taster only, or both alleles. The accuracy of BTD II results have been independently confirmed by two other methods (restriction digestion and DNA sequencing). Thus BTD II provides the easiest and the most efficient way to study the inheritance of PTC sensitivities.

 



 Picture 6

Testing the Hardy-Weinberg Equilibrium

Typing bitter taste sensitivity with PTC filter test has been traditionally used in the class room as one of several easily scored genetic traits. However, results from typing these recessive traits can only identify the probability of recessive allele (t/t) in the class population. The actual distribution of homozygous dominant (T/T) and heterzygous (T/t) individuals cannot be correctly assigned. Instead, q is calculated from the ratio of t/t as q2 under the assumption that the class polulation is in Hardy-Weinberg equilibrium. p is subsequently calculated from 1-q, and the number of T/T and T/t individuals are calculated accordingly.

Consider the following two class data sets. Each class has 50 students and their actual PTC taster genotypes are as indicated. When using classic PTC filter tests, both class has the same ratio of t/t. Without knowing the actual number of T/T and T/t individuals,
p can only be derived under the assumption that class is in H-W equilbrium and q2 equals to 10/50. Red numbers in the H-W columns are the distribution of each genotypes when assuming class is in H-W equilbrium and by deriving from q. As you can see, both classes have different distributions, but PTC filter test cannot reveal their difference (theoretical value pt, qt vs actual values pa, qa in the table below). BTD II provides an easy way to identify accurate numbers of each genotypes, which allows class to perform H-W test to see if your class, school, (or larger population) is in equilbrium.

Picture 10


Conclusion

The Bitter Taster Detector Kit is an excellent educational tool for teaching basic molecular biology skills including genomic DNA isolation, PCR amplification, and gel electrophoresis. It greatly enhances students’ interests in such a way that they will be determining their own genotypes, predicting their own phenotypes, and validating their own DNA testing results with a simple PTC paper test. The kit includes instruction and all the reagents needed for DNA isolation, PCR amplification, and PTC paper test.

Ordering Information

Item Description Item Number Price Purchase Now

Bitter Taster Detector II Complete kit (24 Reactions)

(Includes DNA isolation reagents, swabs, primer set, PCR reagents, and PTC/Control strips for 24 reactions, plus control DNA set)

BTD2-011 130.00

Bitter Taster Detector II Primer Set (100 Reactions)

(Incudes Primer set for 100 reactions, plus control DNA set )

BTD2-021 240.00

DNA Isolation Kit (50 Preps including swabs)

(Includes DNA isolation reagent and swabs for 50 DNA isolation)

BTD2-031 130.00

Bitter Taster Detector II PCR Premix (24 Reactions)

(Includes PCR premix and enzyme for 24 reactions, plus control DNA set)

BTD2-041 98.00

Buccal Swab (50 Packs of 2, sterile)

 

BTD2-051 21.00

PTC Filter and Control Strip Set (100 strips each)

 

BTD2-061 8.00

Higher shipping rate applies to countries outside US and Canada. Please inquire by email to customer_care@alphabiolab.com