U2 Case Studies

Question 1

Huntington’s Disease Case

Answer 1

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

Question 2

Sheep’s Wool Case

Answer 2

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

Question 3

Keratin

Answer 3

Protein that makes up hair, fur, nails, and horns

Question 4

Corn Branching Case

Answer 4

Due to differences in the expression of tb1 gene which encodes for TB1 protein

–>

Question 5

Teosinte

Answer 5

A wild grass ancestor of maize

–> Has > branching than maize

Question 6

tb1 Gene

Answer 6

Teosinte-branched 1 gene

–> Encodes for the transcriptional regulatory protein TB1 (a repressor of transcription of genes required for branching)

Question 7

TB1 Protein

Answer 7

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

Question 8

Teosinte vs Maize

Answer 8

Teosinte = Low expression of tb1 gene (more branching)

Maize = High expression of tb1 gene (less branching)

Question 9

Lactose Intolerance Case

Answer 9

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)

Question 10

Lactase

Answer 10

Enzyme that breaks down lactose (sugar in milk)

Question 11

HD Natural Experiment

Answer 11

Researchers document frequency of HD among communities in Venezuela (a region that had an unusually high amount of HD cases)

Question 12

HD Pedigree Analysis

Answer 12

Scientists collected blood samples from individuals in the Venezuela HD hot zone and made detailed pedigrees of all participants

Question 13

HD Association Study

Answer 13

Investigated the relationship between number of CAG repeats and age of HD onset

–> Found correlation between the two

Question 14

HD Comparison Study

Answer 14

Scientists compared brain scans of people with HD and those without

–> Found differences in the caudate nucleus region of the brain

Question 15

HD Physical Model

Answer 15

Scientists found methods to transplant HD gene into mice to better study the disease

Question 16

HD Conceptual Model

Answer 16

Modeling motor circuitry in HD and other illnesses to improve understanding

Question 17

Different Phenotypes (Case Studies)

Answer 17

True: HD and Sheep Wool

True: Lactose Intolerance and Corn Branching

Question 18

Different Amount of Gene/Protein (Case Studies)

Answer 18

False: HD and Sheep Wool

True: Lactose Intolerance and Corn Branching

Question 19

Different DNA Sequence of Coding Region (Case Studies)

Answer 19

True: HD and Sheep Wool

False: Lactose Intolerance and Corn Branching

Question 20

Different DNA Sequence of NON-Coding Region (Case Studies)

Answer 20

False: HD and Sheep Wool

True: Lactose Intolerance and Corn Branching

Question 21

Different Structure/Function of Protein (Case Studies)

Answer 21

True: HD and Sheep Wool

False: Lactose Intolerance and Corn Branching

Question 22

Differences in Gene Regulatory Switches

Answer 22

False: HD and Sheep Wool

True: Lactose Intolerance and Corn Branching

Question 23

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

Answer 23

4) All of the above

Question 24

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

Answer 24

4) a natural experiment

Question 25

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.

Answer 25

2) This study is an example of an association study.

Question 26

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.

Answer 26

True

Question 27

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.

Answer 27

4) None of the above are true.