Term
What are nonsense codons?
Name them. |
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Definition
Stop codons.
UAA, UAG, UGA |
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Term
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Definition
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Term
| Where does redundancy occur? |
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Definition
| On the 3rd base of a codon. |
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Term
| What are the exceptions to the genetic code being universal? |
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Definition
| Mammalian mitochondria and lower eukaryotes. |
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Term
| What are the 3 types of mutations and what do they produce? |
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Definition
Nonsense mutation - stop codon produced
Missense mutation - different condon produced
Silent mutation - different codon produced but same coding |
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Term
| What is the Shine-Delgarno sequence? |
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Definition
AGGAGG
A signal in prokaryotic mRNA for initiation of translation located 6-10 bases upstream of AUG. Allows for polycistronic mRNA by initiating translation of separate proteins on single mRNA. |
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Term
| How is eukaryotic mRNA translation initiated? |
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Definition
| Translation begins at the first AUG downstream of the Cap. 43S ribosome preinitiation complex tethers to the cap, using a structural feature rather that a sequence feature. |
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Term
| What does wobble refer to? |
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Definition
| The ability of the 1st base of the anticodon to make non-Watson-Crick base pairing with the 3rd base of the codon. |
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Term
| How is translation initiated in prokaryotes? |
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Definition
The first incorporated amino acid is formylmethionine.
• A specific Met-tRNA, f-Met-tRNA , is recognized by the formylation enzyme, which adds a formyl group to the charged methionine.
• Another Met-tRNA, tRNAmet, not recognized by the formylation enzyme is used for incorporation of internal methionine residues.
• The fMet at the N-terminus of the protein is usually enzymatically removed before synthesis of the protein is complete.
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Term
How is translation initiated in eukaryotes?
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Definition
Methionine is the N-terminal residue of the protein. tRNAmet is recognized by the initiation complex and incorporated at the first AUG
• This N-terminus methionine is also often removed from the protein.
• A different Met-tRNA is used for incorporation of internal methionine
residues
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