ABSTRACT
This experiment investigated Mendelian inheritance patterns of phenylthiocarbamide (PTC) tasting in humans. The results were in the expected monohybrid rations of 3 taster: 1 non-taster phenotypes respectively. This supported the hypothesis that the traits were controlled by one gene with two alleles, where T is dominant to t.
INTRODUCTION
Mendel’s Law of Segregation – that two copies of a character (gene) segregate from each other during the formation of gametes, is apparent in the inheritance of PTC tasting in humans (Begg, 1959). The PTC sensory variation was first discovered in the early 1930s by A.L. Fox, which subsequently led to much research. It was reported not long after that PTC tasting is controlled by one gene with two alleles, and that inheritance of these traits is that of Mendel’s monohybrid ration of 3:1. However, there is evidence to suggest transmission of PTC tasting is more complex than this (Kim & Drayna, 2005). The presence of the dominant allele T determines wether or not an individual can taste PTC. A monohybrid cross of two heterozygotes results in three possible genotypes – TT, Tt, and tt, the only non-taster phenotype being tt (Schull, 1948). This study investigated inheritance of PTC tasting in humans to determine wether or not taster and non-taster phenotypes fell into the expected Mendelian ration. It was hypothesised that there would be a ratio of 3 taster: 1 non-taster phenotypes, and that the traits are controlled by one gene with two alleles, where T is dominant to t.
MATERIALS AND METHODS
Data was collected by 3rd year Genetics students. Blank paper and paper containing PTC was given to a total of 110 people. Each person placed the blank paper in his or her mouth and then the paper containing PTC. Afterwards it was recorded wether or not they could taste
