GCSE›AQA GCSE Biology›Mind mapsCell DivisionAQA GCSE Biology: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsChromosomesMade of DNA wrapped around histone proteinsA gene is a section of DNA coding for a proteinHumans have 46 chromosomes (23 pairs)Visible only during divisionCell cycleGrowth: cell enlarges, organelles replicateDNA replication makes sister chromatidsSister chromatids joined at the centromereThen mitosis and cytokinesisMitosisMakes two genetically identical diploid cellsProphase: chromosomes condense, nuclear membrane breaks downMetaphase: chromosomes line up at the equatorAnaphase: sister chromatids pulled apartTelophase: nuclear membranes reform, cytoplasm dividesCell divisioncell cycle, mitosis, meiosisPMAT2nnWhy divide?Growth of multicellular organismsRepair and replacement of damaged cellsAsexual reproduction makes clonesUncontrolled division causes cancerMeiosisMakes four haploid gametes from one diploid cellMeiosis I separates homologous chromosomesMeiosis II separates sister chromatidsCrossing over swaps DNA in prophase IIndependent assortment in metaphase I gives variationExam tipsSay mitosis gives genetically identical daughter cellsRemember stages with PMATCancer: name proto-oncogenes and tumour suppressor genesDon't mix up what separates in meiosis I and II