LectureChapter 10 - From proteins to phenotypesChapter 11 - Mutation

We continued a discussion on pharmacogenetics, or studying phenotypes in terms of how we react to chemicals in our bodies.

We did the popular genetic test on tasting phenylthiocarbamide (PTC), a Mendelian trait easy to diagnose. Some people have the dominant allele that manifests in being able to taste PTC (dubbed "tasters", with the genotype TT or Tt), and some people have only the recessive allele, which prevents them from tasting the chemical compound (dubbed "non-tasters", with genotype tt).  Those who can taste it perceive a bitter flavor.

In our class there were 16 'taster' vs. 6 'non-taster' students.  A fast survey revealed that tasters have a tendency to dislike foods or beverages that have chemicals similar to PTC, like dark beer (question limited to students over 21 years of age), coffee, strong cheeses, artificial sweeteners, and spicy foods. Interestingly enough, most tasters also liked vegetables like broccoli and cabbage, which should be bitter for them.  Non-tasters tended to like such foods and beverages.

We discussed the scope of ecogenetics, the field that studies our responses to chemicals in the environment.

We started the chapter on mutation by providing a definition and outlining the conditions in which a mutation that has a phenotypic effect can be detected.

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Lab 07 - Gene mapping in humans

In Drosophila it is easy to find out if genes are linked, and how closely, since it can be determined by doing experimental crosses and measuring phenotypic frequencies in the offspring (see lab 06). In addition to that, we know exactly what genes are found in specific chromosomes (fruit flies have only four pairs of chromosomes).
In humans it is not that straight forward. Experimental crosses are out of the question, and humans tend to have very few offspring (even large families have very few offspring compared with the potentially thousands of offspring of a Drosophila cross).

In humans, we must rely on pedigrees. In this lab we considered three different pedigrees showing linkage between a genetic disorder and another trait (easily observable). Students learned and practiced how to identify parental and recombinant types in the offpring of each generation, and in the third exercise calculated the odds ratio to determine linkage of traits.

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Lecture, chapter 10 - From proteins to phenotypes

Today we started chapter 10 on how proteins can affect our phenotype.

We started with a brief discussion of protein function and then ways in which mutations can affect our phenotype by causing changes in the sequence of amino acids of enzymes (which may impact metabolic pathways), receptor proteins and transport proteins.  We provided examples using several diseases caused by such mutations.

We started a discussion on pharmacogenetics, or how we can study phenotypes in terms of how we react to chemicals in our bodies.

Up next:  Can you can you not taste phenylthiocarbamide?

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