Dysthrophin Gene; What type of Mutation? - USMLE Forums
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  #1  
Old 07-22-2012
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DNA Dysthrophin Gene; What type of Mutation?

A 3-year-old boy is brought to the pediatrician because he has begun to stumble and has obvious difficulty running, jumping, and climbing stairs. His calf muscles have also become noticeably enlarged. Deletion scanning polymerase chain reaction reveals an absent band from the dystrophin gene after electrophoresis and blotting. Which of the following does the missing band represent?

a) Enhancer
b) Exon
c) Promoter
d) Splice site
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problem in enhancer would effect the rate of transcription but not lead to complete loss of protein
splice site mutations---i can only think of one disease-- beta thalassemia

left with B and C...confused
ill pick C..since deletion of promoter is a/w inability of RNA polymerase to bind the DNA strand and complete loss of transcription activity
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Old 07-22-2012
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I'll pick B. I keep reading about DMD producing a truncated nonfunctional protein due to a frameshift mutation. Promotor mutation wouldn't produce anything.
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Old 07-22-2012
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I looked in my note from Kaplan intense prep.
It said that -splicing defect seen in:
  • Marfan syndrome
  • LDL receptor (type 2 hyperlipidemia)
  • SLE
  • B-thalassemia
  • Tay-Sachs disease
  • Gaucher disease
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I would choose between splice site and exon, but I remember vaguey abnormal Dystrophin was point mutation or sth... So I think splice site.
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Old 07-22-2012
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As far as I know, it's frameshift deletion mutation that results in absence of some of the expressable genes, which is the Exon.
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Splice dire mutation leads to Econ skipping. Exon skipping may lead yo frame shift. Go I'll go Roth exon or splice sit mutation. Complicated though
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i go with B exon
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Quote:
Originally Posted by Casandra View Post
A 3-year-old boy is brought to the pediatrician because he has begun to stumble and has obvious difficulty running, jumping, and climbing stairs. His calf muscles have also become noticeably enlarged. Deletion scanning polymerase chain reaction reveals an absent band from the dystrophin gene after electrophoresis and blotting. Which of the following does the missing band represent?

a) Enhancer
b) Exon
c) Promoter
d) Splice site

exon because express...
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exon , Becker got same gene defective
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Old 07-27-2012
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Default correct answer :)

Correct answer is B) Exon

The mutation that causes Duchenne muscular dystrophy is a deletion in one of the exons, producing a dysfunctional dystrophin protein.
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