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element 6
genetics
Question | Answer |
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Explain the wobble hypothesis in protein synthesis | explains why the third base in a codon may differ and be recognised by the same tRNA and therefore code for the same amino acid. The wobble hypothesis states that the first and second bases must pair in the watson-crick manner but 3rd less constrained |
explain the terms universal and degenerate with reference to the genetic code | The same genetic code is seen in most living organisms so is described as universal. More than one codon exists for each amino acid so the code is degenerate |
Size of ribosomes in prokaryotes | 70s (50s + 30s) |
Size of ribosomes in eukaryotes | 80s (60s + 40s) |
Outline amino acid activation and attachment to tRNA | Amino acid (correct for enzyme) and ATP (giving off pyrophosphate) become adenylated amino acid (AA-AMP). tRNA then replaces the AMP and become aminoacyl tRNA bound by a high energy ester bond (AA-tRNA). Aminoacyl tRNA synthetase catalyses all this. |
Function of modified bases in tRNA | 1. mediate recognition by amino-acyl tRNA synthetase. (different synthetase for each aa) 2. increases number of codons a tRNA can recognise |
Promoter site in prokaryotes | pribnow box (tataat) |