U2 Case Studies Flashcards
Huntington’s Disease Case
Huntingtin Gene: Chromosome 4
–> Contains too many CAG (glutamine AA) repeats (>36)
–> Change to the coding region NOT the non-coding region: Expression of protein is the same, but the protein itself is changed
Sheep’s Wool Case
Different wool types are due to differences in the coding regions that encode for keratin
–> Differing keratin structure = differing wool types
–> No change to non-coding region: Expression of keratin remains the same, but the keratin itself changes
Keratin
Protein that makes up hair, fur, nails, and horns
Corn Branching Case
Due to differences in the expression of tb1 gene which encodes for TB1 protein
–>
Teosinte
A wild grass ancestor of maize
–> Has > branching than maize
tb1 Gene
Teosinte-branched 1 gene
–> Encodes for the transcriptional regulatory protein TB1 (a repressor of transcription of genes required for branching)
TB1 Protein
A repressor of transcription of genes required for branching
> TB1 = < branching
<TB1 = > branching
–> The structure/function of TB1 protein is THE SAME between teosinte and maize
Teosinte vs Maize
Teosinte = Low expression of tb1 gene (more branching)
Maize = High expression of tb1 gene (less branching)
Lactose Intolerance Case
Due to differences in the AMOUNT of lactase enzyme
–> This difference in amount is due to differences in the expression of the lactase gene (a change in the NON CODING region)
–> Encoded by the lactase gene (chromosome 2)
Lactase
Enzyme that breaks down lactose (sugar in milk)
HD Natural Experiment
Researchers document frequency of HD among communities in Venezuela (a region that had an unusually high amount of HD cases)
HD Pedigree Analysis
Scientists collected blood samples from individuals in the Venezuela HD hot zone and made detailed pedigrees of all participants
HD Association Study
Investigated the relationship between number of CAG repeats and age of HD onset
–> Found correlation between the two
HD Comparison Study
Scientists compared brain scans of people with HD and those without
–> Found differences in the caudate nucleus region of the brain
HD Physical Model
Scientists found methods to transplant HD gene into mice to better study the disease
HD Conceptual Model
Modeling motor circuitry in HD and other illnesses to improve understanding
Different Phenotypes (Case Studies)
True: HD and Sheep Wool
True: Lactose Intolerance and Corn Branching
Different Amount of Gene/Protein (Case Studies)
False: HD and Sheep Wool
True: Lactose Intolerance and Corn Branching
Different DNA Sequence of Coding Region (Case Studies)
True: HD and Sheep Wool
False: Lactose Intolerance and Corn Branching
Different DNA Sequence of NON-Coding Region (Case Studies)
False: HD and Sheep Wool
True: Lactose Intolerance and Corn Branching
Different Structure/Function of Protein (Case Studies)
True: HD and Sheep Wool
False: Lactose Intolerance and Corn Branching
Differences in Gene Regulatory Switches
False: HD and Sheep Wool
True: Lactose Intolerance and Corn Branching
Which of the following is true of the Huntingtin protein made in your body?
1) It is translated from mRNA in nerve cells
2) It is possible that my cells have 2 forms of huntingtin with different numbers of glutamine repeats
3) Chemical properties of the amino acids in Huntingtin affect how it interacts with other molecules in the cell
4) All of the above
4) All of the above
A population of humans in which, because of chance, there happens to be a high frequency of a genetic disorder, such as the population Dr. Wexler studied in the Maracaibo area in Venezuela, is an example of:
1) an association study
2) a physical model
3) a conceptual model
4) a natural experiment
5) a causation experiment
4) a natural experiment
To make the graph above, researchers collected data from HD patients on the length of their longer huntingtin CAG repeat (of their two alleles) and the age of onset of the disease (the age at which disease symptoms started).
Which of the following statements is TRUE?
1) The graph shows that higher repeat numbers cause an earlier disease onset.
2) This study is an example of an association study.
3) Both 1 and 2 are true.
4) Neither A nor B are true.
2) This study is an example of an association study.
The study of “normal” brains and those of Huntington’s disease patients indicated that brains in Huntington’s disease patients were inferred to have more neuron death than normal brains.
True
Which of the following is TRUE about the how the nature of science was used to make discoveries about Huntington’s Disease?
1) Dr. Huntington used observations on phenotypes in families to prove that the illness he studied was a genetic disease.
2) Scientists compared normal brains and brains from patients with Huntington’s Disease as physical models to establish that the disease causes degeneration of some brain regions.
3) A patient who does not have a huntingtin allele encoding 40 or more CAG repeats is unlikely to develop Huntington’s Disease. This statement is like a theory.
4) None of the above are true.
4) None of the above are true.
