Lecture 3.ppt - Many sexually reproducing organisms...

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Unformatted text preview: Many sexually reproducing organisms alternate between two states diploid haploid EUKARYOTIC CHROMOSOME : nucleus HOMOLOGOUS CHROMOSOMES: NON-HOMOLOGOUS CHROMOSOMES: MITOSIS: SISTER CHROMATIDS: 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 At Metaphase, sister chromatids are aligned with their kinetochores pointing to opposite poles of the spindle 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! 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 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 During meiotic prophase, homologous chromosomes become physically associated by a combination of crossing over and sister chromatid cohesion. This...
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This note was uploaded on 04/21/2010 for the course BIO 89329 taught by Professor Hollingsworth during the Spring '10 term at SUNY Stony Brook.

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Lecture 3.ppt - Many sexually reproducing organisms...

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