Lecture 3 - Many se xually re producing organism alte s...

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Many sexually reproducing organisms alternate between two states diploid haploid EUKARYOTIC CHROMOSOME : nucleus
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HOMOLOGOUS CHROMOSOMES: NON-HOMOLOGOUS CHROMOSOMES: MITOSIS:
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SISTER CHROMATIDS:
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Sister chromatids are held together by protein complexes called cohesins that are loaded onto the chromosomes during replication. During prophase of mitosis, each pair of sister chromatids condenses to form a highly compact structure that is easier to segregate. Kinetochore or centromere
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At Metaphase, sister chromatids are aligned with their kinetochores pointing to opposite poles of the spindle
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At Anaphase, the cohesin complexes are destroyed and sister chromatids are pulled to opposite poles. After cytokinesis, the result is two genetically identical daughter cells!
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MEIOSIS: The chromosome number is divided by half during meiosis because there are two rounds of chromosome segregation following a single round of chromosome duplication. 2n premeiotic S 4n Meiosis I 2n Meiosis II n Humans 46 premeiotic S 92 Meiosis I 46 Meiosis II 23
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Prior to Meiosis I, chromosome duplication creates sister chromatids connected by sister chromatid cohesion near the centromeres and the arms. 2n 4n Note that a single centromere functions for each pair of sister chromatids
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associated by a combination of crossing over and sister chromatid cohesion. This connection allows homologs to align properly at Metaphase I. 4n
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This note was uploaded on 01/27/2010 for the course BIO 89329 taught by Professor Hollingsworth during the Spring '10 term at SUNY Stony Brook.

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Lecture 3 - Many se xually re producing organism alte s...

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