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

1. Using a Single Nucleotide Polymorphism to Predict Bitter Tasting AbilityLab Overview

2. 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.

3. 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.

4. 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”?

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

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

7. 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.

8. 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.

9. 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.