WBR0310: Difference between revisions
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|AnswerA=Northern blot; 5’(CAG){{sub|n}}3’ probe | |AnswerA=Northern blot; 5’(CAG){{sub|n}}3’ probe | ||
|AnswerAExp=Incorrect: Norther blots are used to detect RNA, not DNA. The patient’s RNA is subjected to electrophoresis and probed with a labeled DNA probe. | |||
|AnswerB=Northern blot; 5’(CTG){{sub|n}}3’ probe | |AnswerB=Northern blot; 5’(CTG){{sub|n}}3’ probe | ||
|AnswerBExp=Incorrect: Norther blots are used to detect RNA, not DNA. The patient’s RNA is subjected to electrophoresis and probed with a labeled DNA probe. | |||
|AnswerC=Southern blot; 5’(CAG){{sub|n}}3’ probe | |AnswerC=Southern blot; 5’(CAG){{sub|n}}3’ probe | ||
|AnswerCExp=Correct: Southern blots are used to detect the presence of certain sequences of DNA. The probe 5’(CAG) n 3’ is the reverse complement of the 5‘CTG 3’ repeat. | |||
|AnswerD=Southern blot; 5’(CTG){{sub|n}}3’ probe | |AnswerD=Southern blot; 5’(CTG){{sub|n}}3’ probe | ||
|AnswerDExp=Incorrect: While 5’ CTG 3’ is the repeat observed in myotonic dystrophy, the reverse complement of 5’ CTG 3’ is 5’ CAG 3’. | |||
|AnswerE=Southern blot; 5’(CAA){{sub|n}}3’ probe | |AnswerE=Southern blot; 5’(CAA){{sub|n}}3’ probe | ||
|Approved= | |AnswerEExp=Incorrect : While Sounther blots are used to detect DNA, 5’ CAA 3’ is the repeat responsible for Friedrich’s ataxia. | ||
|RightAnswer=C | |||
|Approved=Yes | |||
}} | }} | ||
Revision as of 12:56, 5 September 2013
| Author | PageAuthor::William J Gibson |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biochemistry, MainCategory::Genetics |
| Sub Category | SubCategory::General Principles |
| Prompt | [[Prompt::A 25 year old girl presents to her primary care physician complaining of generalized weakness. She reports that the weakness is particularly pronounced in her hands, feet and neck. Furthermore, she reports some difficulty swallowing the multivitamins she takes daily. On further questioning, she admits to greater than normal daytime sleepiness. Past medical history significant is only for occasional gastrointestinal distress over the past 5 years. The young woman reports 3 sexual partners in the last six months. The physician notes that the patient was unable to release her grip after shaking hands. Which of the following techniques would allow a pathologist to confirm the diagnosis from a sample of the patient’s DNA?]] |
| Answer A | [[AnswerA::Northern blot; 5’(CAG)n3’ probe]] |
| Answer A Explanation | AnswerAExp::Incorrect: Norther blots are used to detect RNA, not DNA. The patient’s RNA is subjected to electrophoresis and probed with a labeled DNA probe. |
| Answer B | [[AnswerB::Northern blot; 5’(CTG)n3’ probe]] |
| Answer B Explanation | AnswerBExp::Incorrect: Norther blots are used to detect RNA, not DNA. The patient’s RNA is subjected to electrophoresis and probed with a labeled DNA probe. |
| Answer C | [[AnswerC::Southern blot; 5’(CAG)n3’ probe]] |
| Answer C Explanation | AnswerCExp::Correct: Southern blots are used to detect the presence of certain sequences of DNA. The probe 5’(CAG) n 3’ is the reverse complement of the 5‘CTG 3’ repeat. |
| Answer D | [[AnswerD::Southern blot; 5’(CTG)n3’ probe]] |
| Answer D Explanation | AnswerDExp::Incorrect: While 5’ CTG 3’ is the repeat observed in myotonic dystrophy, the reverse complement of 5’ CTG 3’ is 5’ CAG 3’. |
| Answer E | [[AnswerE::Southern blot; 5’(CAA)n3’ probe]] |
| Answer E Explanation | AnswerEExp::Incorrect : While Sounther blots are used to detect DNA, 5’ CAA 3’ is the repeat responsible for Friedrich’s ataxia. |
| Right Answer | RightAnswer::C |
| Explanation | [[Explanation:: Educational Objective: |
| Approved | Approved::Yes |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |