alleryStart learning →In the Kozak consensus around a vertebrate start codon, which bases can occupy the R position?
AOnly C or U, never A or G
BOnly A or G, never C or U
COnly A or U, never C or G
DOnly C or G, never A or U
Answer & Solution
Correct answer: B. Only A or G, never C or U
1. A eukaryotic initiation complex lands at the 5' cap and tracks along the message looking for AUG.
2. Not every AUG is the right one, and the bases around it decide the matter.
3. The R in the consensus stands for purine.
4. A purine site can be either A or G but cannot be C or U.
5. C and U are the pyrimidines, so the option allowing only those inverts the rule.
6. The closer the surrounding sequence is to the consensus, the higher the efficiency of translation.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 15 "Genes and Proteins", section 15.5 Ribosomes and Protein Synthesis_
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