IB›IB Biology SL›Mind mapsD1.2 Protein synthesisIB Biology SL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsTranscriptionRNA polymerase separates the DNA strandsLinks RNA nucleotides to the template strandBase pairs: A–U, T–A, C–GRNA separates; DNA strands re-pairGene expressionTranscription is a key on/off stageNot all genes are expressed at onceβ-globin transcribed only in red cell precursorsTranslationmRNA binds the small ribosome subunittRNA carries one specific amino acidAnticodon pairs with codon by hydrogen bondsRibosome moves one codon at a timeAmino acids joined by peptide bondsProtein synthesisDNA to polypeptideAUGCGenetic codeTriplet code: 43=644^3 = 6443=64 combinationsDegenerate: 61 codons, 20 amino acidsUniversal in almost all organismsAUG is the start codon (methionine)Three stop codons add no amino acidMutation effectsPoint mutation: no change, one change or early stopSickle cell: GAG → GUG gives valineValine makes haemoglobin form fibres at low oxygenExam tipsRNA has uracil, never thymineConvert DNA template to mRNA before using the codon table