The ability to taste the bitter chemical phenylthiocarbamide (PTC) is an example of dimorphism, a type of polymorphism, with the coexistence of two phenotypes of a character. Most human population are dimorphic, can either detect PTC as a foul, bitter taste or cannot taste it at all. The pedigree in Figure (a) is an example of how two tasters sometimes produce nontaster children.1 According to this pedigree we can conclude that the allele that confers the ability to taste is dominant and that the allele for non tasting is recessive.1
Figure (a): Pedigree for the ability to taste the chemical PTC.
Variation in PTC sensitivity was first discovered in a lab incident in the early 1930s by Arthur L. Fox, an OSHA officer (Fox 1932), when Fox was pouring some PTC powder into a bottle and some “flew around in the air”, a co-worker nearby, C. R. Noller complained that the dust tasted bitter, but Fox insisted he could not taste anything. The two then took turns tasting the PTC powder and found they really differed dramatically in sensitivity. Fox tested “a large number” of people and found a distinct variation was common regardless of age, sex and ethnicity. He classified those people into two categories, those able to taste the PTC at very low concentrations whom he referred to as “tasters” and those unable to taste the PTC except at very high concentrations whom he referred to as “nontasters” or “taste blind”.2 Later several scientists including Fisher, Ford and Huxley (Fisher 1939) and others set out tests for PTC taste sensitivity and the implications of variability of the findings. However, despite almost 70 years of interest, these studies were missing a firm grasp of the molecular genetics of bitter-taste sensitivity.2
When Hoon e...
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...p://search.proquest.com/docview/67470059?accountid=28634. Accessed 4 April 2014.
Drewnowski A, Rock CL. The influence of genetic taste markers on food acceptance. Am J Clin Nutr. 1995 Sep;62(3):506-11. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/7661111. Accessed 4 April 2014.
Navarro-Allende A, Khataan N, El-Sohemy A. (2008). Impact of genetic and environmental determinants of taste with food preferences in older adults. J Nutr Elder. 2008;27(3-4):267-76. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/19042575. Accessed 4 April 2014.
Mangold JE, Payne TJ, Ma JZ et al. Bitter taste receptor gene polymorphisms are an important factor in the development of nicotine dependence in African Americans. J Med Genet. 2008 Sep;45(9):578-82. doi:10.1136/jmg.2008.057844. Epub 2008 Jun 4. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/18524836. Accessed 4 April 2014.
Research on taste aversion in rats led to the discovery that suppression of the immune system can be influenced by:
Modern human brain sizes are significantly smaller than Neanderthal’s and so are their brain cavities. TAS2R38 is the gene that controls taste. For Neanderthals, having a bitter taste “system” could have kept them from poisoning themselves by accident.
Aside from the pedagogical implications of such a striking phenotype, many pioneering studies relating to PTC and the taster/non-taster phenotype have been conducted since its discovery (Wooding 2006). Directly after Fox presented his findings for the National Academy of Sciences, Blakeslee also presented his large-scale study of PTC inheritance within families and saw a similar phenomenon of taster and non-taster phenotypes. Furthermore, Blakeslee classified the tasters according to their taste acuity using dilutions at which the bitte...
Volkows, N. D., & Muenke, M. (2012). Human Genetics. The genetics of addiction, Vol 131(6), 773-777. Retrieved from http://dx.doi.org/10.1007/s00439-012-1173-3
The nature-based view is that expression of addiction (phenotype) is based upon genetic predisposition (genotype). Numerous genetic studies on pedigree have been conducted over the years. The majority of the results of these studies indicate that monozygotic twins have higher concordance of addiction than dizygotic twins. More specifically, the more genes shared, the more similar the propensity for addiction.
A common saying goes, “we are what we eat;” but what exactly that makes us eat in the first place? What are the factors that influence our eating behaviors? If the food that we eat defines our personality and being as a whole, it should then be vital to identify the factors that push us to eat certain kinds of food. I think that social psychology has the answer. As broad as this field may seem, yet this science of explaining human behavior takes it reference on the influence of the environment, people, the media, and almost about anything that can contribute to how people think, feel, and act. In this paper, we will explore the factors that influence our eating
Genetics predispose an individual to having an increased chance of becoming codependent upon drugs or alcohol. Studies of twins and of families that are prone to addiction suggest that about 50% of the risk for drug addiction is genetically based (EBSCOhost). One well-characterized relationship between genes and alcoholism is the result of variation in the liver enzymes that metabolize alcohol (NIH). The result of the liver breaking down the alcohol faster is a higher tolerance. Individuals with a higher tolerance to alcohol, need to drink more than the average person in order to seek the same biological effect. When heavy drinkers suddenly stop or significantly reduce their alcohol consumption, the neurotransmitters prev...
Omnivores are very interesting creatures. We are able to digest most plants and animals and therefore have a wide range of food available to us. However, when faced with new potential foods we are “torn between two conflicting emotions” (Pollan 288). These two emotions are neophilia and neophobia. Pollan defines neophilia as “a risky but necessary openness to new tastes” (288) and neophobia as “a sensible fear of ingesting anything new” (288). These two emotions are easily seen in humans, especially myself. Whenever I am introduced to a new food I immediately feel both of these. I am very tempted to try the new food since it might taste good, but on the other hand it may not taste good and may even give me a stomach-ache or food poisoning. The final decision when trying a new food usually depends on how it looks. In Rozin’s studies, he observed these two emotions in rats. The rats would nibble on the new food and wait to see if it affected them negatively, learning not to eat it if it hurt them. Pollan believed that Rozi...
Ungar, Peter S., and Mark Franklyn Teaford. Human Diet: Its Origin and Evolution. Westport, CT: Bergin & Garvey, 2002. Print.
Western peoples consume enormous per capita quantities of refined sugar because, to most people, very sweet foods taste very good. The existence of the human sweet tooth can be explained, ultimately, as an adaptation of ancestral populations to favor the ripest-and hence the sweetest-fruit. In other words, the selective pressures of times past are most strikingly revealed by the artificial, supernormal stimulus of refined sugar, despite the evidence that eating refined sugar is maladaptive.
Sturgess, Jessica E., et al. "Pharmacogenetics Of Alcohol, Nicotine And Drug Addiction Treatments." Addiction Biology 16.3 (2011): 357-376. Academic Search Complete. Web. 12 Feb. 2014.
Gregor Mendel was an Austrian monk who revolutionized our understanding and perception of genetics. Mendel’s experiments in his monastery garden provided future geneticists with the basic principles of hereditary through the experimentation in both hybrid and pure bred pea plants, which he found to follow specific patterns in their offspring. The choice to use peas was because of their distinct varieties and their ability to produce offspring quickly and the ability to easily regulate fertilization simply with the use of a paintbrush. When conducting these experiments Before Mendel Pea Plant Experimentation it was commonly accepted that a child’s genetic traits were simply half from the mother and half from the father. This evidence was supported by experiments were generally conducted over a short period of time resulting in skewed and unreliable data, whereas Mendel’s experiments were conducted over an eight year period involving tens of thousands of plants. Two of Mendel’s traits that he focused on were the texture of the seed pod. E.g. smooth and round or wrinkled. In the first generation of these plants 100% of the pea plants possessed the Smooth and round texture. On the second generation of the pea plants of every 4 pea plants 3 posessed the smooth trait and a singular pea plant produced wrinkled seeds. Upon the review of his results Mendel concluded that characteristics could be expressed through dominant and recessive traits. The Dominant trait masks or completely covers the recessive, whereas a recessive gene is an allele that is only present in a homozygous genotype. Through Mendel’s experiments he proposed three principles of inheritance, whether you are looking at humans or pea plants, the apparent genetic traits t...
The poor food choices that men and women make is the cause of many illnesses, disease and chronic health conditions. Men and women generally have different thoughts and choices on the topic of healthy food. People’s bad health may be genetically occurred or their exposure to their past nutritional education was not helpful, but their bad health is primarily based upon the poor choices that the individuals choose in daily life.
more than half the variation was found to be due to heredity. Among these traits were
Several sources correlate religion or ethnicity, traditions, advertising and mood as key contributors to the psychological aspect of food consumption. (Citation) explains that for many people their food preferences and eating habits were established during their childhood. As children become exposed to their families culture they learn to value certain foods and adopt specific eating habits that adhere to their cultures beliefs. For example, people are taught at a young age that it’s important to consume three meals a day, commonly referred to as breakfast, lunch and dinner. Many cultures instill this, however there can be variations in the types of food prepared as well as the time of day each meal is