Question
Universal vs nearly universal genetic code
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Answer
The code is nearly universal because mitochondrial and some protozoan codons differ.
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Question
Why do AU-rich elements in the 3′ UTR make an mRNA short-lived?
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Answer
They recruit deadenylation, followed by decapping and rapid 5′→3′ degradation.
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Question
What stabilizes the Watson-Crick double helix?
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Answer
Hydrogen bonding and base-stacking interactions.
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Question
Why does IRP binding have opposite effects on transferrin receptor and ferritin mRNAs?
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Answer
Outcome depends on IRE location: 3′ UTR stabilizes; 5′ UTR blocks translation initiation.
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