BIOL 1411 1st Edition Lecture 15 Outline of Last Lecture I Photosynthesis a Calvin Cycle b C4 photosynthesis c CAM Outline of Current Lecture I The Cell Cycle a Cell Division b Check Points Lecture Cell Division Types of Cell Division o Prokaryotic cells Binary fission as a mechanism of reproduction o Eukaryotic Cells Mitosis as a mechanism of reproduction single cell or growth repair multicellular Meiosis as a mechanism of specialized reproduction cell gametes How they divide o 4 events must occur Reproductive signal Replication of DNA Segregation distribution of the DNA into the two new cells Cytokinesis separation of the two new cells Mitosis o Distinct phases of the cell cycle divided into interphase and mitosis cytokinesis Interphase begins after cytokinesis and ends when mitosis starts The cell nucleus is visible and cell function including DNA replication occurs Interphase divided into 3 sub phases G1 S and G2 defined by DNA replication M phase nuclear membrane dissolves DNA condenses DNA condenses and divides division of the cytoplasm 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 Twice as much DNA in cell during G2 compared to G1 Interphase DNA exists as long threadlike chromatin cell spends most time in interphase o G1 each chromosome consist of 1 dsDNA 1 double helix o S DNA replication produces two identical dsDNA molecules sister chromatids for each chromosome o G2 each chromosome consist of 2 associated dsDNA molecules sister chromatids M Phase chromosomes become visible as dense compact rods each consisting of 2 chromatids held together at the centromere DNA structure o Chromatin packed DNA during histones packed together o Nucleosomes formed by wrapping DNA around histones proteins with positive charges that attract negative phosphate groups of DNA Interaction result in the formation of beadlike units o Condensins coat DNA packing DNA further Phases and Chromosome behavior in mitosis o Prophase protemaphase compaction of replicated DNA into visible chromosomes breakdown of nuclear envelope o Metaphase duplicated chromosomes line up in middle of cell o Anaphase sister chromatids separate and move to opposite sides of cell now daughter chromosomes o Telophase de compaction and formation of new nuclear envelope around the 2 separated sets of daughter chromosomes o Cytokinesis division of the cytoplasm forms 2 cells MTOC microtubule organizing center o Surrounded by high conc Of tubulin dimers o Forms orients the mitotic spindle that will attach to and move the duplicated chromosomes during M phase Centrosome MTOC of animal cells o Consists of 2 centrioles hollow tubes formed by microtubules at right angles o Doubles during S phase too each will move to opposite ends of the nuclear envelope during G2 to M transition o Positions determine the spindle orientation and plane of cell division Plant cells lack centrosomes by have MTOCs Cohesin sister chromatids are held together by this Check Points Control the division of cells Kinases that can regulate processes through the cell cycle cyclin dependent kinases o Check for DNA damage o DNA replication check o Another for damage o Lastly make sure they are attached to spindle Active only when bound to its partnet protein called cyclin
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