Taste + Population Genetics

Taste Receptor 2 (TAS2R38)

Encodes bitter detecting taste receptors found on the tongue

Genotype of Strong Taster and What are the Bands Present?

TT, 177 bp, 44bp

Genotype of Weak Taster and What are the Bands Present?

Tt, 221 bp, 177 bp, 44bp

Genotype of Non-Taster and What are the Bands Present?

tt, 221 bp

PTC (phenylthiocarbamide) Population Stats

70% can taste, 30% can’t taste

Polymorphisms

The variations in DNA sequences among individuals and populations

Polymorphisms in TAS2R38

Single nucleotide polymorphism (SNP)

SNP

Single Base Pair Change

Difference Between PTC Tasters and Non-Tasters

3 amino acids due to 3 SNPs @ distinct locations

Restriction Enzymes

Endonucleases that introduce double stranded cuts in DNA at specific nucleotide sequences, recognizing only their restriction enzyme sites 

Restriction Enzymes used for TAS2R38

HaeIII (Blunt End Cut)

Restriction Fragment Length polymorphisms (RFLP)

Polymorphisms that create a loss or addition of restriction sites

What does the HaeIII cut?

Cuts the restriction site encoded by the dominate allele at 145 bp so that the bands are cut from the PCR product of 221bp

What Does the Dominant Allele Provide?

The restriction site and taste receptors

Biological Evolution

The change in allele proportions within a population over time caused by genetic drift, migration, mutations, selection, and non-random mating

Genetic Drift

Random fluctuation in allele frequencies that occur in small populations by chance

Founder Effect

Individual with a particular allele moves to a new place and starts a new population (ex. Migration)

Genetic Bottleneck

Large loss of population that limits the alleles used for repopulation

Relative Fitness

Measure of a species reproductive success based on its ability to pass on its genotype to the next generation of offspring

Hardy Weinberg Equilibrium Conditions

 No mutations, no migration (gene flow), random mating (organisms all have equal chance to pass their genes), no genetic drift (large populations withstand minor fluctuations in allele frequencies), and no natural selection (equal rate of survival and reproduction)

Equation: Allele Frequencies

p + q = 1

Equation: Genotype Frequencies

p2 + 2pq + q2 = 1