Bitter taste perception is based on one's sensitivity to the chemical compound propylthiouracil (PROP) or similar compounds such as phenylthiocarbamide (PTC). This trait is follows a Mendelian inhertiance pattern in humans and the variations in it's phenotype were first discovered in the 1930s (Wooding, 2006).  These compounds are similar to the "bitterness" some associate with certain foods such as cabbage, dark beers, and brussel sprouts (23andme). The direct phenotype of this trait is the ability to taste the chemical compounds which results in an extremely potent bitter taste vs. those who can not taste the compounds and therefore do not express the phenotype. Today it can easily be determined by placing a strip of paper with the chemical on it on one's tongue to determine if the person in question can taste the chemical or not.

Associated Genes and SNPsEdit


This trait is based on the genotypic variations associated with a single gene, the TAS2R38 gene. This gene normally encodes a receptor that is responsible for detecting the bitter compounds PROP or PTC (23andme). There are two associated SNPs with these gene that lead to the varying phenotypes. The C version of the SNP is considered recessive but when both copies are present in the genotype this inactivates the ability of the receptor to sense the chemical. This then causes the phenotype of not being able to taste the bitter PROP and similar compounds. The G version of the SNP is dominant and when present in one or both copies results in the "ability to taste" phenotype (23andme). 

Conclusions on John Burke's GenotypeEdit

According to DNA sequencing from John Burke's DNA, his genotype was determined to be homozygous recessive for CC and therefore is most likely to display the corresponding phenotype of not being able to taste the compound PROP.


1. Wooding, Stephen. Phenylthiocarbamide: A 75 Year Adventure in Genetics and Natural Selection. Genetics. Apr 2006; 174(4). PubmedID: 1456409

2. Health and Traits- Bitter Taste Perception- Overview. 23andMe Inc. 2007-2014

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