Investigating the prevalence of the TAS2R38 within different ethnicities

Jeff Joy, David Gray, Oliver Fellows, Dr J Rowe, Mr S Lewis.

Abstract: The aim of the project was to use micro pipetting, PCR and electrophoresis in order to identify the presence of specific segments of DNA responsible for sensitivity of (PTC) within different ethnic backgrounds. The genetically controlled ability to taste PTC is coded by the TAS2R38 gene. Individuals with this are sensitive to bitter flavours in foods; like sprouts and cabbage. This investigation was designed to find out how the ethnicity of individuals effected whether or not they can taste PTC. From our investigation, 100% of individuals who were from Asian heritage were either heterozygous or homozygous dominant and only 75% of individuals from European heritage were homozygous recessive. In this investigation, there was only one candidate that was homozygous dominant. Figure 1 – Phenylthiocarbamide Results: Method: Primer concentration: 1: Digested (1 band, digestion of allele for PTC tasting, homozygous taster) (Indian Heritage) 1) Find correct primer in research paper 2: Undigested (1 band, shows DNA extracted successfully) 2) Prepared different concentrations of 3: Digested (2 bands, digestion of allele for PTC tasting, primer using serial dilution. heterozygous taster) (British Heritage) 4: Undigested (1 band, shows DNA extracted successfully) 3) Ran experiment on the same positive 5: Digested (1 band, no digestion of allele for PTC tasting, sample with the varied concentrations for homozygous non-taster) (British Heritage) 3 6: Undigested (1 band, shows DNA extracted successfully) PCR.(5μ mol/dm was determined as the 7: Digested (1 band, no digestion of allele for PTC tasting, most effective) homozygous non-taster) (British Heritage) Sample collection: 8: Undigested (1 band, shows DNA extracted successfully) 9: Digested (1 band, no digestion of allele for PTC tasting, 1) Individuals were asked rinse their mouths homozygous non-taster) (British Heritage) with saline solution. 10: Undigested (1 band, shows DNA extracted successfully) 1 2 3 4 5 6 7 8 9 10 11 11: DNA ladder to compare base pair length 2) Samples were centrifuged to obtain Figure 2 – Electrophoresis gel of samples 1-5 buccal cells

12: Repeated 1 from above PCR: used to replicate specific sequences 13: Repeated 3 from above of DNA with an associated primer. 14: Digested (1 band, no digestion of allele for PTC tasting, 1) The DNA primer mix should be added to homozygous non-taster) (Hungarian Heritage) 15: Undigested (1 band, shows DNA extracted successfully) 0.2ml reaction tube. 16: Digested (2 bands, digestion of allele for PTC tasting, 2) Samples are placed in a PCR machine to heterozygous taster) (Chinese Heritage) 17: Undigested (1 band, shows DNA extracted successfully) replicate the indicated base sequence. 18: Digested (2 bands, digestion of allele for PTC tasting, 3) Samples are frozen to prevent destruction heterozygous taster) (Chinese Heritage) of DNA. 19: Undigested (1 band, shows DNA extracted successfully) 20: DNA ladder Gel Electrophoresis: used to separate out 21: DNA ladder 12 13 14 15 16 17 18 19 20 21 DNA samples according to the DNA lengths. Figure 3 – Electrophoresis gel of samples 6-8 1) Prepare an electrophoresis gel. 2) Pipette samples into the gel and run it. This causes bands to form on the gel.

Conclusion: The results showed that 75% of the samples from European origin were Homozygous recessive (non-tasters) while 100% of the samples from Asian origin were Heterozygous or Homozygous Dominant (tasting).Only 1 out of the 9 samples were Homozygous dominant. When comparing the results to the global trend it can be seen that in our investigation only 44% of samples could taste PTC compared to approximately 75% globally. This suggests that the distribution of tasters maybe uneven. In future investigation the use of more samples from a greater variety of regions could lead to more conclusive findings. Additionally, the use European Asian of a statistical test could be used to Homozygous - 3 0 validate the results to show significance, Recessive as well as testing whether individuals Heterozygous 1 3 Key that had the allele for tasting PTC could Homozygous recessive – Homozygous - Heterozygous – actually taste it. 0 1 Dominant Homozygous dominant – Figure 4 – Table of results Figure 5 – World map showing distribution of results

References: • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4467798/ Used to identify primer Acknowledgements: • https://learn.genetics.utah.edu/content/basics/ptc/ Used to find percentage of people that can taste PTC