PTC Taster Genomic Analysis Lab Report
Laboratory Goals: 1. Determine Taster Phenotype 2. Isolate DNA from each individual 3. Determine Taster Genotype
If I am a taster, then my genotype for PTC taster must be either TT (homozygous dominant) or Tt (heterozygous)
I – Results:
This experiment aimed to investigate the allele frequency of the PTC taster gene (TAS2R38) in a small population, represented by the students in class. The genotype obtained from genomic analysis (via PCR and gel electrophoresis) confirmed that the genotypic result is consistent with the phenotypic result observed at the beginning of the lab.
However, DNA fragments of 3 lab subjects didn’t show up on the gel. The allele…show more content… The 64bp fragments are faint and not visible. According to the profile for PTC gene in 18 individual: 8 heterozygous tasters (Tt), 2 homozygous tasters (TT) and 8 homozygous recessive non-tasters (tt). (Figure 4)
| Individual (N=1) | Class (N= 21) | | Expected | Observed | Expected | Observed | Phenotype | Taster | 0.75 | 1 | 15.75 | 11 | | Non-Taster | 0.25 | 0 | 5.25 | 10 | Genotype | TT | 0.25 | 0 | 5.25 | 2 | | Tt | 0.50 | 1 | 10.5 | 8 | | tt | 0.25 | 0 | 5.25 | 8 |
* genotype was undetermined for 3 individuals due to lack of data.
Figure 1. Tally of the class’ genomic analysis for PTC taster gene.
II – Discussion:
Receptor proteins recognize bitter-tasting compounds on the surface of taste cells. There are approximately 30 genes for different bitter taste receptors. The gene for the PTC taste receptor, TAS2R38, was identified in 2003. Sequencing identified three nucleotide positions that vary within the human population (Kim et al.); each variable position is termed a single nucleotide polymorphism (SNP). One specific combination of the three SNPs, termed a haplotype, correlates most strongly with tasting ability. In this lab, non-tasters (homozygous recessive, tt) can determine their genotype without having to run the PCR and electrophoresis because non-taster gene is recessive. Thus, the only way for them to express recessive phenotype is to have the tt alleles of