Lecture, chapter 10 - From proteins to phenotypes: Pharmacogenetics

Today we finished chapter 10, from proteins to genotypes. Specifically we talked about pharmacogenetics

There are phenotypes that become obvious only when people are exposed to chemicals. Whether they are drugs, chemicals in the environment, or chemicals in products we consume (food, clothing, etc.), different allele combinations make us more or less sensitive to exposure.

We talket about the first pharmcogenetic trait, discoverd in the 1930s, the ability or inability to taste PTC. This trait is trivial, but it has implications that have lead research that may find connections between sensitivity to certain tastes, diet, and obesity.
We also talkes about how between 100 and 1000 cel membrane proteins dictate our ability to smell or not smell certain chemicals. So many enzymes, most of which most likely have several alleles, and so many possible allele combinations make us virtually unique in our olfactory capacity.

In terms of sensitivity to chemicals in the environment, especially pesticides, it is ecogenetics the subfield that deals wit our genetic-based differences in sensitivity. Research is being done in many populations to determine safe levels of exposure to different chemicals. Such research involves an important genetic component.

On Monday: We will start chapter 11, on mutation as the source of genetc variation.

Reminder: Next Friday, May 01, we will have our second exam. over chapters 8, 9, 10, and 11, plus elements of our genetic mapping labs (both in human and Drosophila). Bring a calculator!

----------------------

Lecture, chapter 10 - From proteins to phenotypes

Today we covered most of chapter 10, from proteins to genotypes.

We talked about how mutations in genes that encode for transport proteins can be reflected in the phenotype. Our main example was hemoglobin. Mutations in the genes thay encode for any of the subunits of the protein can cause a variety of genetic disorders (hemoglobin variants, thalassemias) which most common symptom is anemia.

One of the better known cases is sickle cell anemia, caused by a mutation in the beta globins of hemoglobin, causing them to come become insoluble, resulting in the aggregation of the protein, therefore altering the shape of red blood cells and making them brittle.

Tomorrow: We'll finish chapter 10, covering the section on pharmacogenetics.

----------------------

Lab 07 - Human gene mapping

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

In humans, we have to rely on pedigrees. In this lab we considered three different pedigrees showing linkage between a genetic disorder and another trait. 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.

----------------------

Lecture, chapters 9 and 10 - From genes to proteins, and from proteins to phenotypes

Today we finished chapter 9, on how genetic information is used to synthesize proteins, and started chapter 10, on how proteins are, or influence, the phenotype.

We talked about the possibilities of changing a polypeptide after it has been synthesized, thus accounting fopr the more than 100,000 enzymes in the human organism, which has just about 25,000 genes in its genome. We defined the difference between a polypeptide and a protein (hint: every protein is a polypeptide or a group of polypeptides, but not every polypeptide is a protein).
Then we talked about the levels of structure that proteins can have: Primary, secondary, tertiary, and, in some cases, quaternary. We finished the chapter by discussing some of the consequences of a mutation that alters the amino acid sequence of a protein.

We also started chapter 10, and discussed how certain mutations in the sequence of amino acids of enzymes and receptor proteins affect the phenotype of the person who bearing them.

----------------------