GCSE›AQA GCSE Biology›Mind mapsReproduction and DNAAQA GCSE Biology: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsReproductionSexual: two parents, gametes fuse, varied offspringAsexual: one parent, mitosis, identical clonesSexual is slower but lets populations adaptAsexual is fast but vulnerable to changeCausing variationMeiosis shuffles chromosomes into new combinationsCrossing over swaps DNA segmentsFertilisation mixes alleles from two parentsMitosis copies DNA unchangedDNA structureDouble helix of two nucleotide strandsNucleotide: sugar, phosphate, baseSugar-phosphate backbone joins nucleotidesA-T and C-G complementary base pairsStrands held by hydrogen bondsDNAreproduction and genesATCGGenetic codeA gene codes for a sequence of amino acidsThree bases (a codon) code for one amino acidCode is degenerate and universalAUG is the start codonUAA, UAG, UGA are stop codonsMaking a proteinHigher Tier: transcription copies DNA to mRNA in the nucleusRNA polymerase pairs U with AmRNA meets a ribosome for translationtRNA anticodons match mRNA codonsAmino acids joined by peptide bondsGenome projectMaps all human genes: about 20,000-25,000Sequenced roughly 3 billion base pairsHelps find genes behind genetic diseasesEnables personalised medicine and gene therapy