Bio 201 1st Edition Lecture 27Outline of Last Lecture I. The Cell Cycle CheckpointsA. Tumor Suppressor GenesB. Cell DeathC. OncogenesD. Leading to CancerOutline of Current LectureI. MitosisA. Steps of MitosisB. Spindle StructureC. Spindle FunctionCurrent LectureI. Mitosis-Condensation of DNA is required for mitosis to occur without error, it prevents tangling and breakage of chromosomes when cells divide-DNA is a double stranded helix and super coiled, it wraps around histone and is wound again. -Cdk1 phosphorylates histone proteins-30nm fiber chromatin in interphase cells, and 700 nm fiber chromatin in mitosis. -Homologous chromosomes- Same chromosomes inherited from either the father or the mother (same genes, but not identical because different alleles)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-Chromatid- One copy of a replicated chromosome-Sister Chromatids- 2 identical copies of a replicated chromosome-Centromere- Location somewhere within a chromosome where sister chromatids are joinedA. Steps of Mitosis1. Duplication of centrosomes2. Condensation of chromosomes3. Nuclear envelope breakdown4. Metaphase plate- Alignment of chromosomes5. Segregation of sister chromatids into daughter cells6. Cytokinesis- separation of daughter cellsB. Spindle Structure- Made up of 3 microtubules-Kinetochore MT- Bind to chromosome at + end and centromere at – end.-Astral MT- Connected to membrane at + end and centrosome at – end. -Polar MT- Connected through kinesin-like motor proteins at + end and centrosome at – end. -Spindles from by MT polymerization from centrosome, MT that run into kinetochore become kinetochore MT. MT that run into the membrane become astral MT, and MT that run into other MT become polar MT. -Cohesin- A kinetochore protein that holds sister chromatids together(cohesive). At anaphase cohesion breaks down allowing the sister chromatids to separate. C. Spindle Function--Looking to cure cancer, scientists used taxol which stabilizes MT. It inhibits MT depolymerization, which is needed for completion of mitosis. Taxol causes sister chromatids to stay together. -MT depolymerization and motor proteins of kinetochore MTs, pull chromatids toward centrosome. Dynein-like motor proteins pull chromatids towards – ends. KinetochoreMTs depolymerize at both + and – ends chromosomes pulled towards daughter cell centrosomes. -MT depolymerization and motor proteins of astral and polar MT push daughter cells apart.- Astral MT depolymerization at + end while dynein-like motor proteins pull on MT centrosome gets pulled towards membrane.-Polar MT polymerize at + end while kinesin-like proteins push MTs apart centrosome gets pulled
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