Meiosis 1 and 2 0.0 / 5 ? BiologyCellular processes and structureA2/A-levelOCR Created by: Steff06Created on: 26-04-16 20:38 What type of cells divide by meiosis? Sex cells/gametes 1 of 27 What happens to chromatin in prophase 1? Chromatin condenses and forms visible chromosomes. Forms pairs of homologous chromosomes. 2 of 27 What makes up the pair? A maternal and paternal chromosome. 3 of 27 How are 2 sister chromatids joined? By the centromere. 4 of 27 What happens to non-sister chromatids? Become intertwined and form cross-overs known as chiasmata. 5 of 27 What is there an exchange of due to this crossing over? Genetic material. 6 of 27 What is crossing-over and what does it create? It is random and can happen anywhere along the length of the chromosome. It creates genetic variation. 7 of 27 What happens to the structure of the cell? Nuclear envelope breaks down and spindle fibres form. 8 of 27 What do the chromosomes do in metaphase 1? Chromosomes line up down the middle of the cell (equator). 9 of 27 How do the chromosomes line up in the middle? Bivalent pairs line up down the equator together. 10 of 27 Describe the orientation of pairs of chromosomes on each spindle It is random and provides genetic variation. 11 of 27 What happens to the chromosomes in anaphase 1? Homologous pairs of chromosomes are pulled to opposite poles of the cell. 12 of 27 What do chiasmata do and what happens regarding cross over? Chiasmata separate and lengths of chromatid that have been crossed over remain within the chromatid to which they have become newly attached. 13 of 27 In telophase 1, what happens inside the cell? Spindle fibres disintegrate and nuclear membrane reforms. 14 of 27 Where do the envelopes form? An envelope forms around each set of chromosomes at each pole. 15 of 27 How does the cell divide? By cytokinesis. 16 of 27 What do the chromosomes do? They uncoil. 17 of 27 Prophase 2 where do the cells members come from? Possess 1 member from each pair of homologous chromosomes (haploid). 18 of 27 Describe what happens inside the cell Nuclear membrane disintegrates and chromosomes condense. Spindle fibres begin to form. 19 of 27 What do the chromosomes do in metaphase 2? Chromosomes line up independently along the equator of the spindle. 20 of 27 What happens to the sister chromatids? They separate. 21 of 27 Where are the chromosomes attached? Attached to spindle fibres at centromeres. 22 of 27 How are the chromatids arranged? Chromatids of each chromosome are randomly arranged. 23 of 27 In anaphase 2, what do the centrioles do and what does this allow? Centrioles replicate which allows the chromatids to repel each other. 24 of 27 What does spindle activity do? Spindle activity pulls chromatids to opposite poles of the cell. 25 of 27 What do the centromeres and chromatids do? Centromeres divide and chromatids randomly segregate. 26 of 27 In telophase 2, what do the cells do and what is produced? Each cell divides into 2. Four genetically different cells are produced as a result of meiosis. 27 of 27
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