GCSE›AQA GCSE Biology›Mind mapsGenetic InheritanceAQA GCSE Biology: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsWhat is DNA?Polymer of two strands in a double helixFound in chromosomes in the nucleusBuilt from nucleotides: sugar, phosphate and a baseFour bases: A, C, G, TGenes and genomeA gene is a short section of DNAEach gene codes for one proteinThree bases (triplet) code for one amino acidGenome is all of an organism's DNAHuman genome mapped: helps trace disease genesInheritanceDNA, genes and genomesACGTDNA to proteinBase order sets amino acid order (HT)Amino acid order determines the protein made (HT)Coding and non-coding DNA both affect phenotype (HT)Non-coding DNA can switch genes on or off (HT)HistoryMendel bred pea plants: inherited 'units'Later: chromosomes seen in cell divisionUnits and chromosomes found to behave alike: genesMid-20th century: DNA structure foundExam tipsGenotype is the DNA; phenotype is what you seeMendel ignored because no chromosome or DNA evidence yetNever say 'no one believed him'