meiosis biology 0.0 / 5 ? ScienceThe human bodyGCSEEdexcel Created by: revisionprodigyCreated on: 03-04-15 20:14 definition MEIOSIS: DIVISION OF A PARENT CELL THAT PRODUCES GENETICALLY DIFFERENT HAPLOID CELLS 1 of 10 stage one STAGE ONE each chromosome duplicates to become double stranded (like in mitosis) each strand is called a chromatid 2 of 10 stage two STAGE TWO each chromosome becomes thicker, shorter and more visible. then chromatids are then joined at the centromere. the nuclear envelope disappears 3 of 10 stage three STAGE THREE spindle fibres spread out from each end of the cell and attach to the centromere of each chromosome similar* chromosomes then pair up in the centre of the cell *the scientific word homologous can be used 4 of 10 STAGE FOUR STAGE FOUR Small parts of the homologous chromosomes cross over this exchage of genetic material increases variation (eventually creating the different haploid cells) 5 of 10 stage five STAGE FIVE the spindle fibres contract, seperating the homologous pair into opposite sides of the cell, which begins to divide each chromosome is still formed of two chromatids 6 of 10 stage six STAGE SIX a new nuclear envelope forms around each set of chromosomes and the cell finishes dividing each cell only has 46 chromosomes 7 of 10 STAGE SEVEN STAGE SEVEN The 2nd part of meiosis begins with the chromosomes condensing again and the nuclear envelopes disapearing 8 of 10 stage eight STAGE EIGHT spindle fibres spread out at right angles and attach to the chromosomes. the fibres contract, seperating the two chromatids in each chromosome. Each cell divides in two. 9 of 10 stage NINE STAGE NINE a new nuclear envelope forms around each set of chromosomes. each cell contains 23 chromosomes and each chromosome is genetically different. 10 of 10
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