Investigating families with hormone deficiencies
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- Investigating families with hormone deficiencies
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Investigating families with hormone deficiencies
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[ID] => 553787
[post_author] => 12815
[post_date] => 2024-12-23 06:26:21
[post_date_gmt] => 2024-12-23 11:26:21
[post_content] => Practice Passage (Question 1-6)
*This passage is the property of Khan Academy and has been reformatted into an AAMC-style interface in their entirety by MedLife Mastery. MedLife Mastery does not endorse and is not an affiliate of Khan Academy.
Hormone A is a protein that induces normal cells to release more chloride ions (Cl⁻⁻) into the extracellular space. To examine the mechanism of Hormone A, researchers screened hundreds of families for inherited deficiencies in Hormone A-induced calcium release. They found two unrelated families in which many males, but no females, had a defect in their ability to respond to Hormone A.
The researchers performed a series of experiments on cells isolated from affected males and unaffected females from each of the families. They wanted to determine: (A) the mechanism that related the binding of Hormone A and Cl⁻⁻ release in a normal cell, and (B) the point in the mechanism where the defect occurs in affected males. They obtained the following results:
- In both families, none of the cell isolates from affected males had an elevated efflux of CI⁻⁻ after the addition of Hormone A.
- Hormone A was bound to Protein X of all of the isolated cells examined.
- Protein X was smaller than normal in cells from affected males in Family 1, but its size was normal in all other cells examined.
- In whole cells, Protein X phosphorylated Protein Y in the cells of females only.
- When Protein X was isolated in its active form from females, it phosphorylated Protein Y isolated from the affected males of Family 1, but not Family 2.
- Phosphorylated Protein Y was necessary and sufficient to increase the rate of CI⁻⁻ efflux in cells isolated from females.
[post_title] => Investigating families with hormone deficiencies
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[questions] => Array
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[0] => Array
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[quiz_unique_key] => 602779517
[question] => Based on the passage, what does the mutation in the gene for affected males from Family 2 most likely result in?
[value] => Array
(
[answer] => 4
[description] => Reason for Correct Answer:
Hormone A was bound to protein X in all of the isolates.
The data states that Protein X appeared smaller than normal in Family 1 but normal in Family 2.
Normal Protein X from females could not phosphorylate Protein Y in the males in Family 2.
Thus, there was likely a mutation affecting Protein Y such that it could not be phosphorylated – such as a mutation resulting in the replacement of a single amino acid in Protein Y.
)
[answers] => Array
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[0] => Array
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[each_answer] => A. The introduction of a premature stop codon in Hormone A.
)
[1] => Array
(
[each_answer] => B. The introduction of a premature stop codon in Protein X.
)
[2] => Array
(
[each_answer] => C. The replacement of a single amino acid in Protein X.
)
[3] => Array
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[each_answer] => D. The replacement of a single amino acid in Protein Y.
)
)
)
[1] => Array
(
[quiz_unique_key] => 3243476205
[question] => Which of the following proteins is most likely to utilize ATP for its action?
[value] => Array
(
[answer] => 2
[description] => Reason for Correct Answer:
ATP would be used by the enzyme that is phosphorylating another enzyme.
The data reveal that Protein Y is the protein that becomes phosphorylated in Hormone-A induced chloride transport, and this phosphorylation is necessary and sufficient to increase chloride efflux.
The data say that Protein X isolated from healthy females phosphorylates Protein Y.
This means that Protein X is a kinase that uses ATP to phosphorylate Protein Y.
)
[answers] => Array
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[0] => Array
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[each_answer] => A. Hormone A
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[1] => Array
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[each_answer] => B. Protein X
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[2] => Array
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[each_answer] => C. Protein Y
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[3] => Array
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[each_answer] => D. Both Hormone A and Protein Y
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[2] => Array
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[quiz_unique_key] => 2187790141
[question] => In the normal cellular response to Hormone A, the efflux of CI⁻⁻ should immediately stop after which step?
[value] => Array
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[answer] => 4
[description] => Reason for Correct Answer:
Hormone A binds to Protein X to induce a response, which leads to the efflux of CI⁻⁻.
Protein X is not phosphorylated as part of this process.
The efflux of CI⁻⁻ will stop the quickest when Hormone A is no longer bound to Protein X, out of all of the answer choices. Termination of Protein X synthesis would take a longer time to have an effect, and the exocytosis of the Protein X-Hormone A complex is not something the passage suggests would happen.
)
[answers] => Array
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[0] => Array
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[each_answer] => A. The complex of Hormone A and Protein X undergoes endocytosis
)
[1] => Array
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[each_answer] => B. Protein X is dephosphorylated
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[2] => Array
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[each_answer] => C. Synthesis of Protein X is terminated
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[3] => Array
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[each_answer] => D. Hormone A no longer binds to Protein X
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[3] => Array
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[quiz_unique_key] => 1579828684
[question] => What is the most likely function of phosphorylated Protein Y?
[value] => Array
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[answer] => 2
[description] => Reason for Correct Answer:
Hormone A binds to Protein X to induce a response.
The response is that Protein X phosphorylates Protein Y.
Phosphorylated Protein Y results in the efflux of CI⁻⁻ from the cell, thus it is likely a membrane channel protein.
)
[answers] => Array
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[0] => Array
(
[each_answer] => A. Phosphatase
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[1] => Array
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[each_answer] => B. Membrane channel
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[2] => Array
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[each_answer] => C. Antibody
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[each_answer] => D. Hormone receptor
)
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[4] => Array
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[quiz_unique_key] => 1498560436
[question] => Which children of an affected male and a homozygous healthy female will most likely inherit the deficiency, assuming that Hormone A activity is X-linked recessive?
[value] => Array
(
[answer] => 4
[description] => Reason for Correct Answer:
X-linked traits are located on the X chromosome.
Males pass on their X chromosome to their female offspring and their Y chromosome to their male offspring.
Since males cannot inherit the X chromosome from their father, they will not be affected
Since the females will inherit a healthy X chromosome from their mother, they will also not be affected.
)
[answers] => Array
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[0] => Array
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[each_answer] => A. All of the males and all of the females
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[each_answer] => B. Half of the males and half of the females
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[2] => Array
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[each_answer] => C. All of the males and half of the females
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[each_answer] => D. None of the males and none of the females
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[553787|1] => D
[553787|2] => B
[553787|3] => D
[553787|4] => B
[553787|5] => D
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