WBR0144: Difference between revisions

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(Created page with "{{WBRQuestion |QuestionAuthor={{Rim}} |ExamType=USMLE Step 1 |MainCategory=Genetics |SubCategory=Musculoskeletal/Rheumatology |MainCategory=Genetics |SubCategory=Musculoskelet...")
 
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|MainCategory=Genetics
|MainCategory=Genetics
|SubCategory=Musculoskeletal/Rheumatology
|SubCategory=Musculoskeletal/Rheumatology
|Prompt=A 37-year-old male presented to the emergency departement for severe sudden chest pain that is tearing in nature and radiating to the back.  The patient is tall, has abnormal joints laxity and long extremities and limbs.  A medical student was suggesting that this patient has Marfan syndrome, whereas the resident in the ER was arguing that these features of long extremities and joint laxity could be found in other inherited conditions.  Which of the following can explain the resident’s argument?
|Prompt=A 37-year-old male presented to the emergency department for severe sudden chest pain that is tearing in nature and radiating to the back.  The patient is tall, has abnormal joints laxity and long extremities and limbs.  A medical student was suggesting that this patient has Marfan syndrome, whereas the resident in the ER was arguing that these features of long extremities and joint laxity could be found in other inherited conditions.  Which of the following can explain the resident’s argument?
|Explanation=Educational objective: [[Marfanoid habitus]] can be caused by [[Marfan syndrome]], [[homocysteinuria]] or [[MEN 2 B syndrome]].  This is an example of locus heterogeneity.
|Explanation=Educational objective: [[Marfanoid habitus]] can be caused by [[Marfan syndrome]], [[homocysteinuria]] or [[Multiple endocrine neoplasia type 2|MEN 2 B syndrome]].  This is an example of locus heterogeneity.
|AnswerA=Mosaicism
|AnswerA=Mosaicism
|AnswerAExp=[[Mosaicism]] denotes the presence of two or more populations of cells with different [[genotypes]] in one individual who has developed from a single [[fertilized egg]].  
|AnswerAExp=[[Mosaicism]] denotes the presence of two or more populations of cells with different [[genotypes]] in one individual who has developed from a single [[fertilized egg]].  
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|AnswerBExp=[[Heteroplasmy]] is the presence of a mixture of more than one type of an organellar genome (mitochondrial DNA (mtDNA) or plastid DNA) within a cell or individual.  It is a factor for the severity of [[mitochondrial disease]]s.  
|AnswerBExp=[[Heteroplasmy]] is the presence of a mixture of more than one type of an organellar genome (mitochondrial DNA (mtDNA) or plastid DNA) within a cell or individual.  It is a factor for the severity of [[mitochondrial disease]]s.  
|AnswerC=Pleiotropy
|AnswerC=Pleiotropy
|AnswerCExp=[[Pleiotropy]] occurs when one gene influences multiple phenotypic traits.  Consequently, a mutation in a pleiotropic gene may have an effect on some or all traits simultaneously.
|AnswerCExp=Pleiotropy occurs when one gene influences multiple phenotypic traits.  Consequently, a mutation in a pleiotropic gene may have an effect on some or all traits simultaneously.
|AnswerD=Locus heterogeneity
|AnswerD=Locus heterogeneity
|AnswerDExp=[[Locus heterogeneity]] is a single disorder, trait, or pattern of traits caused by mutations in genes at different chromosomal loci. This patient’s [[marfanoid]] habitus can be caused by [[Marfan syndrome]], [[homocysteinuria]] or [[MEN 2 B syndrome]].
|AnswerDExp=Locus heterogeneity is a single disorder, trait, or pattern of traits caused by mutations in genes at different chromosomal loci. This patient’s [[marfanoid]] habitus can be caused by [[Marfan syndrome]], [[homocysteinuria]] or [[Multiple endocrine neoplasia type 2|MEN 2 B syndrome]].
|AnswerE=Variable expression
|AnswerE=Variable expression
|AnswerEExp=[[Variable expression]] occurs when a phenotype is expressed to a different degree among individuals with the same genotype.
|AnswerEExp=Variable expression occurs when a phenotype is expressed to a different degree among individuals with the same genotype.
|RightAnswer=D
|RightAnswer=D
|Approved=No
|Approved=No
}}
}}

Revision as of 01:43, 27 August 2013
Author [[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Genetics
Sub Category SubCategory::Musculoskeletal/Rheumatology
Prompt [[Prompt::A 37-year-old male presented to the emergency department for severe sudden chest pain that is tearing in nature and radiating to the back. The patient is tall, has abnormal joints laxity and long extremities and limbs. A medical student was suggesting that this patient has Marfan syndrome, whereas the resident in the ER was arguing that these features of long extremities and joint laxity could be found in other inherited conditions. Which of the following can explain the resident’s argument?]]
Answer A AnswerA::Mosaicism
Answer A Explanation [[AnswerAExp::Mosaicism denotes the presence of two or more populations of cells with different genotypes in one individual who has developed from a single fertilized egg.

Different types of mosaicism exist, such as gonadal mosaicism (restricted to the gametes) or tissue or somatic mosaicism.]]

Answer B AnswerB::Heteroplasmy
Answer B Explanation [[AnswerBExp::Heteroplasmy is the presence of a mixture of more than one type of an organellar genome (mitochondrial DNA (mtDNA) or plastid DNA) within a cell or individual. It is a factor for the severity of mitochondrial diseases.]]
Answer C AnswerC::Pleiotropy
Answer C Explanation AnswerCExp::Pleiotropy occurs when one gene influences multiple phenotypic traits. Consequently, a mutation in a pleiotropic gene may have an effect on some or all traits simultaneously.
Answer D AnswerD::Locus heterogeneity
Answer D Explanation [[AnswerDExp::Locus heterogeneity is a single disorder, trait, or pattern of traits caused by mutations in genes at different chromosomal loci. This patient’s marfanoid habitus can be caused by Marfan syndrome, homocysteinuria or MEN 2 B syndrome.]]
Answer E AnswerE::Variable expression
Answer E Explanation AnswerEExp::Variable expression occurs when a phenotype is expressed to a different degree among individuals with the same genotype.
Right Answer RightAnswer::D
Explanation [[Explanation::Educational objective: Marfanoid habitus can be caused by Marfan syndrome, homocysteinuria or MEN 2 B syndrome. This is an example of locus heterogeneity.

Educational Objective:
References: ]]

Approved Approved::No
Keyword
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