biol lec 2

biol lec 2 - Diplotene Means double ribbon Sister...

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· Diplotene · Means double ribbon · Sister chromatids begin to separate · Some regions of contact remain between sister chromatids · Chiasma: place on tetrad where 2 non-sister chromatids have exchanged genetic material via crossing over · Crossing over: occurs in pachytene -visible only during diplotene -serves 2 purposes: 1) results in a new combination of genes (genetic variability) 2) physical structure (chiasmata) hold tetrads together Diakinesis · Means moves apart · Chromosomes pull further apart · Non-sister chromatids remain loosely associated at chiasmata · Nucleolus and nuclear envelope break down · 2 centromeres (kinetochores) of each tetrad become attached to the spindle fibers Metaphase 1 of meiosis · Each pair of homologs takes up a position on metaphase plate · Sister centromeres orient to same pole · Homologous centromeres orient to opposite poles · Both sister chromatids are set up to be pulled in the same direction
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biol lec 2 - Diplotene Means double ribbon Sister...

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