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Discussion Starter · #1 ·
A genetic disease in which there's a complete loss of enzyme activity. A northern blot was done on tissue sample and revealed normal enzyme amount. What could explain the genetic defect?
-Gene mutation
-Splicing mutation
-Promotor mutation
-Transcriptional defect
-Nonsense mutation
-Silent mutation
-Missense mutation
-Postranslational defect
 

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Because the northern blot is normal (which means mRNA is normal) then I'd choose post-translation defect as the correct answer.
 

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Discussion Starter · #4 ·
post-translational is not the correct answer
because such defects usually do not cause complete enzyme deficiency
Try another one :)
 

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It's not even missense mutation because mis sense mutation just causes an amino acid replacement and the enzyme may be still functional.
The correct answer is nonsense mutation which causes a non functional enzyme.
 

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but won't nonsense mutation give a truncated protein via a stop codon formation? northern blot will be negative me thinks
 

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but won't nonsense mutation give a truncated protein via a stop codon formation? northern blot will be negative me thinks
mRNA will be completely transcribed as usual and develop into mature mRNA the stop codon will be encountered during the translation process and the protein will be truncated and non functional.
 

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I don't get it, isn't Northern blot test supposed to detect RNA sequence too. Or just the length.
:eek:
Blotting will not occur if the probe is not complementary to the mRNA sequence. So yes it detects correct sequence mRNA strands!!
I think the question is designed wrong. They should say normal amount of mRNA and they should not say normal Northern blot.
I think I've seen a similar question in Kaplan Qbank that had a similar theme and concept and I think they mentioned just mRNA they did not say Northern blot.
 
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