Using a Single Nucleotide Polymorphism to Predict Bitter Tasting Ability Lab Overview

Step 1: Isolating DNA The gene of interest in the experiment, TAS2R38, is located on chromosome #7. This gene is associated with our ability to taste a chemical called PTC. In the lab, you will isolate a sample of your DNA from your own cheek cells.

Step 2: Amplifying the Gene of Interest Using your DNA sample, you will amplify a 220 base pair region of the PTC gene using PCR. –Specific primers attach to either side of the target sequence In this lab, you will investigate one of the base pair changes or single nucleotide polymorphisms (SNPs) that affects a person’s ability to taste the chemical PTC.

Genetics Review – Question 1 The inability to taste PTC is a recessive trait. If a capital “T” is is used to designate the dominant allele and a lowercase “t” is used to designate the recessive allele, what is the genotype of a “Nontaster”?

Answer A “Nontaster” carries two recessive alleles and thus has the genotype “tt”.

Genetics Review – Question 2 What are the possible genotypes for a “Taster”?

Answer A “Taster” may be homozygous dominant with a genotype of “TT” or heterozygous with a genotype of “Tt”. In this lab, you will use the tools of molecular biology to determine your genotype for PTC tasting.

Step 3: Restriction Analysis Restriction enzymes, molecular scissors, recognize specific DNA sequences and cut the nucleotide strands. In this part of the experiment, you will use a specific restriction enzyme, HaeIII, to identify a SNP or base pair difference in the amplified segment of the PTC tasting gene.

Step 4: Gel Electrophoresis Gel Electrophoresis separates DNA fragments based on their molecular weight. Once you have digested your DNA sample with the restriction enzymes, run your product on a gel to analyze your results.