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|MainCategory=Genetics
|MainCategory=Genetics
|SubCategory=General Principles
|SubCategory=General Principles
|Prompt=A geneticist is studying the process of aging in rat cells. He reports finding specific G-rich regions that undergo single strand breaks following oxidative damage. Based on his experiment, he shows that these regions reflect the replicative potential and the biological age of cells based on the cumulative oxidative damage sustained by these somatic cells. Which regions of DNA are most likely referred to by the geneticist?
|Prompt=A geneticist studying the process of aging in rat cells reports finding specific G-rich regions that undergo single strand breaks following oxidative damage. Based on his experiment, he shows that these regions reflect the replicative potential and the biological age of cells based on the cumulative oxidative damage sustained by these somatic cells. Which of the following regions of DNA are most likely referred to by the geneticist?
|Explanation=Telomeres are specific regions located at the end of the DNA. The regulation mechanisms of both telomere length and replication are significant for the integrity of the genome. Telomeres are important regions because they have a role in cell senescence and the replicative potential of cells. The length of telomeres is regulated by telomerase and by the replication fork itself. If telomerases are absent, the length of telomeres is shortened with every replication until. Once the length reaches a lower limit, replicative senescence, called Hayflick limit, is induced. Additionally, G-rich overhanging regions at the end of telomeres are susceptible to oxidative damage, whose cumulative effects is associated with the biological age of somatic cells.
|Explanation=Telomeres are specific regions located at the end of the DNA. The regulation mechanisms of both the telomere length and replication are significant for the integrity of the genome. Telomeres have a role in cell senescence and the replicative potential of cells. The length of telomeres is regulated by telomerase and by the replication fork itself. If telomerases are absent, the lengths of telomeres are shortened with every replication until the length reaches the lower limit, the replicative senescence (the Hayflick limit), is induced. Additionally, G-rich overhanging regions at the end of telomeres are susceptible to oxidative damage, whose cumulative effects is associated with the biological age of somatic cells.


Educational Objective:
|EducationalObjectives= Telomeres are important for the replicative potential of cells and for identifying the biological age of somatic cells.
Telomeres are important for the replicative potential of cells and for identifying the biological age of somatic cells.


References:
|References= Salpea KD, Humphries SE. Telomere length in atherosclerosis and diabetes. Atherosclerosis. 2010; 209(1):35-38.
Salpea KD, Humphries SE. Telomere length in atherosclerosis and diabetes. Atherosclerosis. 2010; 209(1):35-38.


Waga S, Stillman B. The DNA replication fork in eukaryotic cells. Annu. Rev. Biochem. 1998; 67:721-51.
Waga S, Stillman B. The DNA replication fork in eukaryotic cells. Annu. Rev. Biochem. 1998; 67:721-51.
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|AnswerCExp=Promoters are specific regions of DNA where RNA polymerase and transcription factors bind to DNA. They are located upstream of the transcribed sequence.
|AnswerCExp=Promoters are specific regions of DNA where RNA polymerase and transcription factors bind to DNA. They are located upstream of the transcribed sequence.
|AnswerD=Telomeres
|AnswerD=Telomeres
|AnswerDExp=Telomeres are specific regions on DNA that play a role in the replicative potential of cells and cell senescence.
|AnswerDExp=Telomeres are specific regions on DNA that play a role in the replicative potential of cells and cell senescences.
|AnswerE=Enhancers
|AnswerE=Enhancers
|AnswerEExp=Enhancers are specific regions on DNA that bind to transcription factors and alter gene expression. They are located anywhere along or outside the transcribed DNA region.
|AnswerEExp=Enhancers are specific regions on DNA that bind to transcription factors and alter gene expression. They are located anywhere along or outside the transcribed DNA region.
|RightAnswer=D
|RightAnswer=D
|WBRKeyword=telomere, length, replicative, potential, replication, age, cell, senescence, biological, G-rich, oxidative, damage
|WBRKeyword=telomere, length, replicative, potential, replication, age, cell, senescence, biological, G-rich, oxidative, damage, transcription, DNA, RNA
|Approved=No
|Approved=Yes
}}
}}

Revision as of 12:56, 14 July 2014
Author [[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Genetics
Sub Category SubCategory::General Principles
Prompt [[Prompt::A geneticist studying the process of aging in rat cells reports finding specific G-rich regions that undergo single strand breaks following oxidative damage. Based on his experiment, he shows that these regions reflect the replicative potential and the biological age of cells based on the cumulative oxidative damage sustained by these somatic cells. Which of the following regions of DNA are most likely referred to by the geneticist?]]
Answer A AnswerA::Exons
Answer A Explanation AnswerAExp::Exons are coding regions of DNA.
Answer B AnswerB::Introns
Answer B Explanation AnswerBExp::Introns are non-coding regions of DNA.
Answer C AnswerC::Promoters
Answer C Explanation AnswerCExp::Promoters are specific regions of DNA where RNA polymerase and transcription factors bind to DNA. They are located upstream of the transcribed sequence.
Answer D AnswerD::Telomeres
Answer D Explanation AnswerDExp::Telomeres are specific regions on DNA that play a role in the replicative potential of cells and cell senescences.
Answer E AnswerE::Enhancers
Answer E Explanation AnswerEExp::Enhancers are specific regions on DNA that bind to transcription factors and alter gene expression. They are located anywhere along or outside the transcribed DNA region.
Right Answer RightAnswer::D
Explanation [[Explanation::Telomeres are specific regions located at the end of the DNA. The regulation mechanisms of both the telomere length and replication are significant for the integrity of the genome. Telomeres have a role in cell senescence and the replicative potential of cells. The length of telomeres is regulated by telomerase and by the replication fork itself. If telomerases are absent, the lengths of telomeres are shortened with every replication until the length reaches the lower limit, the replicative senescence (the Hayflick limit), is induced. Additionally, G-rich overhanging regions at the end of telomeres are susceptible to oxidative damage, whose cumulative effects is associated with the biological age of somatic cells.

Educational Objective: Telomeres are important for the replicative potential of cells and for identifying the biological age of somatic cells.
References: Salpea KD, Humphries SE. Telomere length in atherosclerosis and diabetes. Atherosclerosis. 2010; 209(1):35-38.

Waga S, Stillman B. The DNA replication fork in eukaryotic cells. Annu. Rev. Biochem. 1998; 67:721-51.]]

Approved Approved::Yes
Keyword WBRKeyword::telomere, WBRKeyword::length, WBRKeyword::replicative, WBRKeyword::potential, WBRKeyword::replication, WBRKeyword::age, WBRKeyword::cell, WBRKeyword::senescence, WBRKeyword::biological, WBRKeyword::G-rich, WBRKeyword::oxidative, WBRKeyword::damage, WBRKeyword::transcription, WBRKeyword::DNA, WBRKeyword::RNA
Linked Question Linked::
Order in Linked Questions LinkedOrder::
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