BIO 171 1st Edition Lecture 3 Outline of Last Lecture I. The Scientific Method II. Standard ErrorIII. Experimental Design Outline of Current Lecture I. Organization of DNA Within CellsII. Cell Division III. The Eukaryotic Cell Cycle IV. Phases of Mitosis V. MeiosisVI. Multicellular Organisms Current LectureOrganization of DNA Within Cells-In Prokaryotes:oNO nucleusoDNA contained within cell membrane but floats around freely-In Eukaryotes:oALL have a nucleus (which contains linear DNA)oMitochondria and Chloroplasts contain circular DNA-Cell division in Eukaryotes is much more complex than in Prokaryotes because DNA is located within the nuclear envelope-DNA is then looped and packaged tightly together to form chromatin, which packs together to form chromosomesoChromosome= two sister (identical) chromatids attached at a centromere -As soon as sister chromatids are no longer attached, they are referred to as sister chromosomes 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.oWhen chromosomes condense, they adopt specific characteristics which make them identifiable under a microscope (i.e the "X" shape shown in most images)oA Karyotype is a layout of all the different chromosomes representative of a species (humans have 46: 22 pairs of homologous chromosomes and 1 pair of sex chromosomes)-Haploid cells (n) contain one complete set of chromosomes -Diploid cells (2n) contain two complete sets of chromosomes (i.e. humans) Cell Division-= the process by which cells make more cells -Is essential for continual growth and healing (creates the billions of cells that are found in multicellular organisms)-Involves two main parts:1. Replication of DNA2. DNA copies to make two daughter cells -Two types of cell division1. Mitosis= Eukaryotic cell division (during M Phase of cell cycle)2. Meiosis= Germ cell (or sex cell) division to produce gametes The Eukaryotic Cell Cycle-Occurs between one cell division and the next -Two distinct phases:1. M Phase= parent cell dividing into two daughter cells 2. Interphase= cell makes preparations for division -M Phase 1. Includes Mitosis and Cytokinesis-Mitosis- division of stuff inside nucleus (DNA/chromosomes)-Cytokinesis- division of the cytoplasm-Both go hand in hand with one anotheroInterphase1. Includes G1 Phase, S Phase, and G2 Phase 2. G1 Phase= cell grows and gains proteins (preparing for S Phase) 3. S Phase= DNA synthesis-DNA that is packed into chromosomes is replicated producing two copies of homologous (identical) chromosomes within the nucleus 4. G2 Phase= second growth phase so cells can prepare for M Phase Mitosis (phases of)-Prophase:oNuclear envelope disappears, replicated chromatin fibers condense into chromosomes-Metaphase: oChromosomes line up in the middle of the cell equidistant from two poles preparing to be separated oCentromeres (which pull chromosomes apart during mitosis) attach to centromeres-Anaphase:oPaired chromosomes (sister chromatids) separate at the centromere as the centrosomes pull each to opposite poles of the cell-Telophase:oNewly separated sister chromatids (chromosomes) are at opposite ends of cell and become chromosomes within nuclei of two identical daughter cellsoNew cells are able to from because of Cytokinesis happening simultaneously, dividing the cytoplasm of the cell oNew daughter cells begin interphase and start cell cycle for themselvesMeiosis-Germ cell (sex cell) division which produces gametes (sperm and egg cells)-Asexual reproduction= When one parent produces genetically identical offspring (cloning) oLeads to a faster population increase than sexual reproduction does (doesn't require a mate) oRequires less energy/resources-Sexual reproduction= When two individuals combine their genetic information to produce genetically diverse offspring oAllows for more genetic diversity oAbility to remove bad mutations -Phases of Meiosis:oMeiosis 1- A diploid germ cell divides and produces two haploid cells-Cell begins in interphase (like during mitosis) where cell grows and DNA isreplicated -Prophase 1 = nuclear envelope disappears, chromatin condenses into chromosomes, homologous chromosomes line up next to one another (preparing for crossing over to occur)Crossing over= homologous chromosomes (one from mom and one from dad) exchange sections of DNA -Metaphase 1 = Nuclear envelope gone, chromosomes line up in center ofcell, spindle fibers of centrosomes begin to attach to centromeres -Anaphase 1 = Spindle fibers pull homologous pairs of chromosomes apart (do not pull sister chromatids apart lie during mitosis) toward opposite poles of cell -Telophase 1 = Chromosomes are separated to opposite poles of cell Cytokinesis happens toward end of telophase 1, separating cytoplasm of cell into two new haploid cells (only one complete set of chromosomes) - new nuclear envelopes formoMeiosis 2- Two haploid cells divide to produce four haploid gametes (phases similar to mitosis)-Includes Prophase 2, Metaphase 2, Anaphase 2, and Telophase 2Phases analogous to stages that occur during mitosis -Once four gamete cells are produced, fertilization can occur oFertilization= haploid gamete cells (one sperm and one egg) fuse together to form one diploid zygote, which grows and eventually forms a multicellular organism Multicellular Organisms -Complex multicellular organisms have structures specialized for bulk transport (the means by which molecules move through organisms at rates beyond those possible by diffusion)-General requirements for multicellular life:oCells must stick togetheroCells must communicate with each otheroCells must participate in a network of genetic interactions that regulate division and differentiation -Development is the product of molecular communication between