Chapter 15 Notes
Chapter 15 Notes BIOL 2601 - 01
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BIOL 2601 - 01
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This 6 page Class Notes was uploaded by Suzanne Notetaker on Friday October 23, 2015. The Class Notes belongs to BIOL 2601 - 01 at Youngstown State University taught by Dr. Asch in Fall 2015. Since its upload, it has received 24 views. For similar materials see General Biology in Biology at Youngstown State University.
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Date Created: 10/23/15
Chapter 15 The Eukaryotic Cell Cycle Every cell originates from another cell All organisms produced by repeated round of cell growth and division In Eukaryotes cell division via mitosis and meiosis Eukarvotic Chromosomes Cytogenetics microscopic examination of chromosomes and cell division When cells ready to divide chromosomes become compact to be seen with light microscope Karyotype reveals number size and form of chromosomes Set of Chromosomes Humans have 23 pairs of chromosomes Autosomes922 pairs in humans Sex chromosomes l pair in humans XX or XY Ploidy Diploid or 2n9humans have 23 pairs of chromosomes 46 total chromosomes Haploid or n9 gametes have 1 member of each pair of chromosomes 23 total chromosomes Homologues Diploid species members of pair of chromosomes homologous chromosomes Autosomes each homologue nearly identical in size and genetic composition Sex chromosomes 9X and Y are very different from each other size and composition Cell Cycle Interphase G1first gap Ssynthesis of DNA G2second gap Mmitosis and cytokinesis Gosubstitutes for G1 for cells postponing division or never dividing again G1 Phase cell growth occurs signaling molecules cause cell to accumulate changes promote progression Pass restriction point G1 checkpoint9move to S phase S Phase chromosomes replicate Sister chromatidsonly in S Phase9two copies stayed joined to each other G1946 chromosomes G2946 pairs of sister chromatids 92 chromatids G2 Phase cell synthesizes proteins needed during mitosis and cytokinesis Mitosis division of one cell nucleus into two with separation of sister chromatids Cytokinesis divide cytoplasm into two daughter cells Decision to Divide 1 External factors environmental conditions and signaling molecules 2 Internal factors cell cycle control molecules and checkpoints Checkpoint Proteins cyclins or cdks see chapter 14 responsible for advancing cell through the cell cycle s phases Three Checkpoints critical regulatory points act as sensors to determine if cell can divide 1 G1 checkpoint restriction point 2 G2 checkpoint 3 Metaphase checkpoint Cycle delayed until problem fixed Loss of checkpoints can lead to mutationcancer Mitotic Cell Division cell divides to produce two new cells genetically identical to original involves mitosis and cytokinesis Preparation for Cell Division 1 Each chromosome replicates prior to mitosis Kinetochore Centromere a region of DNA beneath ldnetochore proteins 2 At the start of mitosis the chromosomes become compact a Chromosome replication b Schematic drawing of a and compaction metaphase chromosome One One chromatid chromatid Pair of sister chromatids Image from Biology Authors Brooker Widmaier Graham and Stiling Copyright The McGraw Hill Companies Inc Mitotic spindle ensures daughter cell Will obtain correct number and type of chromosomes organizesort chromosomes during mitosis Centrosomes9microtubule organizing center duplicates at M phase composed of Spindle Microtubules spindle formed from microtubules microtubules formed from tubulin proteins Types 1 Astral 2 Polar 3 Kinetochore Outline of Cell Division Interphase Mitosis Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis Mitosis separate sister chromatids 1 Prophase a Chromosomes replicated and joined as sister chromatids b Nuclear membrane dissociates c Chromatids condense into highly compacted structures 2 Prometaphase Nuclear envelope fragments Mitotic spindle formed Centrosomes move apart and demarcate two poles Spindle fibers interact with sister chromatids Two kinetochores are attached to kinetochore microtubules from opposite poles 3 Metaphase a Pairs of sister chromatids align along plane halfway between poles metaphase platesingle row 4 Anaphase a Connections broken between sister chromatids and pulled toward opposite poles where they attach 5 Telophase a Chromosomes reach their poles and decondense b Nuclear membranes refrom to produce two separate nuclei 9999 s Cytokinesis two nuclei segregated into separate daughter cells division of rest of the cell Different in animals and plants Animals cleavage furrow constricts to separate cells Plants cell plate forms cell wall between two daughter cells Meiosis and Sexual Reproduction Sexual reproduction requires fertilization event where two haploid gametes unite to create diploid cell called zygote Original diploid haploid gametes diploid cell zygote Meiosis9process by which haploid cells are produced from a cell that was originally diploid Gx phase prior to meiosis r A diploid cell Homologous pair 2 y of chromosomes prior to chromosomal 7 replication 39 39 1 Chromosomes replicate during S phase and then new I condense at the start of meiosis Diploid cell with replicated l and condensed chromosomes Sister chromatids 2 Homologous A chromosomes separate Haplmd cells with pairs of sister chromatids Meiosis II 3 Sister chromatids separate i I Image from Biology Authors Brooker Widmaier Graham and Stiling Copyright The McGraw Hill Companies Inc Meiosis goes through cell cycle like mitosis Two key differences homologous pairs form a bivalent or tetrad and crossing over 1 Bivalent or tetrad homologous pairs of sister chromatids associate With each other to form process called Synapsis a Synaptonemal complexprotein structure that connects homologous chromosomes 2 Crossing Over physical exchange between chromosome pieces of the crossing bivalent a Chiasmaarms of chromosomes separate but remain adhered to crossover site ister chromatids Chiasma Bivalent Homologs Synaptonemal complex forming 1 Homologous 2 Synapsis begins 3 Bivalems form 4 Crossing over 5 The Chiasma becomes chromosomes occurs Visible as chromosome condense anus separate luring late propluse Image from Biology Authors Brooker Widmaier Graham and Stiling Copyright The McGraw Hill Companies Inc Meiosis I Prophase I chromosomes condense bivalents form and nuclear membrane breaks down Prometaphase I chromatids attach to kinetochore microtubules pairs of sister chromatids attached to SINGLE pole Metaphase I bivalents organized along metaphase plate as double row promote genetic diversity Anaphase I segregation of homologous occurs Telophase I sister chromatids reach their poles and decondense nuclear membrane reform C okinesis End of meiosis I two haploid cells With no pairs of homologous chromosomes Meiosis I in ame ummu gm onphase Tmll m 4 me sewn MA mmudmodmpdes Image from Biology Authors Brooker Widmaier Graham and Stiling Copyright The McGraw Hill Companies Inc Meiosis II No S phase between meiosis I and meiosis II Sorting events similar to mitosis Anaphase II separate sister chromatids ZMeiosis 11 Owen 9W1 MWE oan GJTebphsenudqDo nals WWW mwmmmmm me n mm Mathewaim W sides poles Wu m menn19 Mupm eZCdkmlw s Image from Biology Authors Brooker Widmaier Graham and Stiling Copyright The McGraw Hill Companies Inc Meiosis and Mitosis Mitosis produces two diploid daughter cells Meiosis produces four haploid daughter cells Life Cycle sequence of events produce another generation of organisms For sexual reproduction involves alternation between haploids and diploids Diploid dominant species most animal species haploid gametes specialized type of cell Haploid dominant species fungi and protists multicellular organism haploid Altemation of generations plants and some algae intermediate dominance multicellular diploidsporophyte multicellular haploidgametophyte Variation in Chromosome Structure and Number can have major effects on organisms human diseases important in evolution Chromosomes variation rare abnormal Chromosomes composition Within a given species tends to remain constant Chromosomes identification 1 Size 2 Location of centromere 3 Bending pattern Chromosomal Mutations 1 Deletions segment of chromosomes missing 2 Duplications repeated segment 3 Inversions segment change direction 4 Translocations segment attach to another chromosome Changes in Chromosomes Number 1 Euploid normal number of chromosomes 2 Polypoid 3 or more sets of chromosomes 3 Aneuploidy abnormal number a Trisomic normal 2 copies of chromosomes p1us 3rd b Monosomic missing one of normal copies of chromosome c Imbalance in level of gene expression
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