Bios 208 1st Edition Lecture 26Outline of Last Lecture I. Cyclic Electron FlowII. A Comparison of Chemiosmosis in Chloroplasts and MitochondriaIII. C4 PlantsIV. CAM PlantsV. The Importance of Photosynthesis: A ReviewOutline of Current Lecture I. The Key Roles of Cell DivisionII. Binary Fission in BacteriaIII. Cellular Organization of the Genetic MaterialIV. Distribution of Chromosomes During Eukaryotic Cell DivisionV. Phases of the Cell CycleVI. CytokinesisVII. The Evolution of MitosisCurrent LectureI. The Key Roles of Cell DivisionA. The ability of organisms to produce more of their own kind best distinguishes living things from nonliving matterB. The continuity of life is based on the reproduction of cells, or cell divisionC. In unicellular organisms, division of one cell reproduces the entire organismD. Multicellular organisms depend on cell division fora) Development from a fertilized cellb) Growthc) RepairE. Cell division is an integral part of the cell cycle, the life of a cell from formation to its owndivisionII. Binary Fission in BacteriaA. Prokaryotes (bacteria and archaea) reproduce by a type of cell division called binary fissionThese 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.B. In binary fission, the chromosome replicates (beginning at the origin of replication), and the two daughter chromosomes actively move apartC. The plasma membrane pinches inward, dividing the cell into twoIII. Cellular Organization of the Genetic MaterialA. All the DNA in a cell constitutes the cell’s genomeB. A genome can consist of a single DNA molecule (common in prokaryotic cells) or a number of DNA molecules (common in eukaryotic cells)C. DNA molecules in a cell are packaged into chromosomesD. Eukaryotic chromosomes consist of chromatin, a complex of DNA and protein that condenses during cell divisionE. Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus; Humans have 46.F. Somatic cells (non-reproductive cells) have two sets of chromosomesG. Gametes (reproductive cells: sperm and eggs) have half as many chromosomes as somatic cellsIV. Distribution of Chromosomes During Eukaryotic Cell DivisionA. In preparation for cell division, DNA is replicated and the chromosomes condenseB. Each duplicated chromosome has two sister chromatids (joined copies of the original chromosome), which separate during cell divisionC. The centromere is the narrow “waist” of the duplicated chromosome, where the two chromatids are most closely attachedD. During cell division, the two sister chromatids of each duplicated chromosome separate and move into two nucleiE. Once separate, the chromatids are called chromosomesF. Eukaryotic cell division consists of;a) Mitosis, the division of the genetic material in the nucleusb) Cytokinesis, the division of the cytoplasmG. Gametes are produced by a variation of cell division called meiosisH. Meiosis yields nonidentical daughter cells that have only one set of chromosomes, half as many as the parent cellI. In 1882, the German anatomist Walther Flemming developed dyes to observe chromosomes during mitosis and cytokinesisV. Phases of the Cell CycleA. The cell cycle consists ofa) Mitotic (M) phase (mitosis and cytokinesis)B. Interphase (cell growth and copying of chromosomes in preparation for cell division)Interphase (about 90% of the cell cycle) can be divided into sub-phasesa) G1 phase (“first gap”)b) S phase (“synthesis”)c) G2 phase (“second gap”)C. The cell grows during all three phases, but chromosomes are duplicated only during the S phaseD. Mitosis is conventionally divided into five phasesa) Prophaseb) Prometaphasec) Metaphased) Anaphasee) TelophaseE. Cytokinesis overlaps the latter stages of mitosisF. The Mitotic Spindlea) The mitotic spindle is a structure made of microtubules that controls chromosome movement during mitosisb) In animal cells, assembly of spindle microtubules begins in the centrosome, the microtubule organizing centerc) The centrosome replicates during interphase, forming two centrosomes that migrateto opposite ends of the cell during prophase and prometaphased) An aster (a radial array of short microtubules) extends from each centrosomee) The spindle includes the centrosomes, the spindle microtubules, and the astersG. Pro-metaphase and Metaphasea) During pro-metaphase, some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomesb) Kinetochores are protein complexes associated with centromeresc) At metaphase, the chromosomes are all lined up at the metaphase plate, an imaginary structure at the midway point between the spindle’s two polesH. Anaphasea) In anaphase, sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cellb) The kinetochore contains motor proteins that “walk along” the microtubules, pulling the chromosomes.c) The microtubules shorten by depolymerizing at their kinetochore endsd) An analogy is climbing up a rope that is deteriorating underneath you! This can be seen by experiments marking the microtubules e) Non-kinetochore microtubules from opposite poles overlap and push against each other, elongating the cellA. Telophasea) In telophase, genetically identical daughter nuclei form at opposite ends of the cellb) Cytokinesis (visible cell division) begins during anaphase or telophase and the spindle apparatus eventually disassembles.VI. CytokinesisA. In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrowB. In plant cells, a cell plate forms during cytokinesisVII. The Evolution of MitosisA. Since prokaryotes evolved before eukaryotes, mitosis probably evolved from binary fissionB. Certain protists exhibit types of cell division that seem intermediate between binary fission and mitosisC. The eukaryotic cell cycle is regulated by a molecular control systemD. The frequency of cell division varies with the type of cellE. These differences result from regulation at the molecular levelF. Cancer cells manage to escape the usual controls on the cell cycleG. The cell cycle appears to be driven by specific chemical signals present in the cytoplasmH. Some evidence for this hypothesis comes from experiments in which cultured mammalian cells at different phases of the cell cycle were fused to form a single cell withtwo