1/30/2012. Objectives. Functions of ER. Functions of Golgi Complex. Protein Degradation. DNA Replication. DNA Replication

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1 Objectives Review ER & Golgi Complex DNA replicatio Fuctios of ER Proteis to be secreted are made by ribosomes of rough ER Cotai a leader sequece of 30+ hydrophobic amio acids that directs proteis to eter ER Iside ER leader sequece is removed; protei is modified Fuctios of Golgi Complex Secretory proteis leave ER i vesicles ad go to Golgi Complex I Golgi complex carbohydrates are added to make glycoproteis Vesicles leave Golgi for lysosomes or exocytosis Protei Degradatio Ezyme activity (& regulatory proteis) is cotrolled by degradig them: By proteases i lysosomes By proteasomes i cytoplasm Proteasomes (large ezyme complexes) ubiquiti tags mark proteis to be degraded DNA Replicatio Prior to cells dividig, DNA replicates itself ad idetical copies go to 2 daughter cells The Process of DNA replicatio: Helicase: breaks hydroge bods to produce 2 free strads of DNA Primase: established a RNA primer of RNA ucleotides DNA polymerase : bids to each strad ad makes ew complemetary copy of old strad Usig A-T, C-G pairig rules Thus each copy is composed of 1 ew strad ad 1 old strad (called semi-coservative replicatio) Origial DNA sequece is preserved Primase sets up short sequece of RNA ucleotides 3. DNA Polymerase adds complimetary Nucleotides (5 to 3) 4. RNA Primer is replaced with DNA ucleotides DNA Replicatio 1. Helicase breaks H bods 5. DNA ligase jois segmets together

2 DNA Replicatio Icomig ucleotides Cotiuous 2. Primase - RNA Primer!!!! Paretal DNA (a) Replicatio fork (b) 3. DNA polymerase (e) Discotiuous Please ote that due to differig operatig systems, some aimatios will ot appear util the presetatio is viewed i Presetatio Mode (Slide i the Normal or Slide Sorter views. All aimatios will appear after viewig i Presetatio Mode ad playig each aimatio. Most aimatios will require the latest versio of the Flash Player, 1. DNA helicase Key A T (c) Gap i (d) C G replicatio 5. DNA ligase 4. Replace RNA primer Okazaki fragmets Errors ad Mutatios DNA polymerase does make mistakes But: teds to replace icorrect, biochemically ustable pairs thus, oly 1 real error per 1 billio bases replicated DNA mutatios: because of replicatio errors or evirometal factors some mutatios = o problem/some big problem Please ote that due to differig operatig systems, some aimatios will ot appear util the presetatio is viewed i Presetatio Mode (Slide i the Normal or Slide Sorter views. All aimatios will appear after viewig i Presetatio Mode ad playig each aimatio. Most aimatios will require the latest versio of the Flash Player, 4-9 Cell Cycle Most cells of body are i iterphase, the odividig stage of life cycle Iterphase is subdivided ito: G 1 - cell performs ormal physiological roles S - DNA is replicated i preparatio for divisio G 2 - chromati codeses prior to divisio Please ote that due to differig operatig systems, some aimatios will ot appear util the presetatio is viewed i Presetatio Mode (Slide i the Normal or Slide Sorter views. All aimatios will appear after viewig i Presetatio Mode ad playig each aimatio. Most aimatios will require the latest versio of the Flash Player,

3 Cell divisio occurs i all body cells (except eggs ad sperm) Fuctios of mitosis: growth of tissues replacemet of cells that die repair of damaged tissues 4 phases of mitosis prophase, metaphase, aaphase, telophase Whe the cell divides Chromosome codese ad duplicate Cosist of 2 duplicate strads called chromatids coected by a cetromere (M phase) (M phase) Role of Cetrosome I prophase chromosomes become visible distict structures I metaphase chromosomes lie up sigle file alog equator Positioed by spidle fibers I aaphase cetromeres split Spidle fibers pull each chromatid to opposite poles I telophase cytoplasm is divided (= cytokiesis), producig 2 daughter cells Aimal cells have a cetrosome located ear ucleus i iterphase Cotais 2 cetrioles Role of Cetrosome (M phase) Cetrosome is duplicated i G 1 if cell is goig to divide Replicates move to opposite poles by metaphase Microtubules grow from cetrosomes to form spidle fibers - attach to cetromeres of chromosomes Spidle fibers pull chromosomes to opposite poles durig aaphase

4 Telomeres Please ote that due to differig operatig systems, some aimatios will ot appear util the presetatio is viewed i Presetatio Mode (Slide i the Normal or Slide Sorter views. All aimatios will appear after viewig i Presetatio Mode ad playig each aimatio. Most aimatios will require the latest versio of the Flash Player, No-codig regios of DNA at eds of chromosomes Each time cell divides, a legth of telomere is lost Because DNA polymerase ca t copy the very ed of DNA strad Whe telomere is used up, cell becomes seescet Believed to represet a molecular clock for agig - That ticks dow with each divisio - Trigger for apoptosis?? 3-67 Telomeres Germial ad cacer cells ca divide idefiitely ad do ot age Have the ezyme telomerase which replaces telomere ucleotides ot duplicated durig DNA replicatio Cyclis Cyclis: Proteis that promote differet phases of cell cycle Accumulate prior to mitosis Destroyed durig cell divisio Promotes phases to occur ad cotiue Ocogees: gees whose mutatios are associated with cacer Tumor suppressor gees ihibit cacer developmet Tumor suppressor gee p53 (trascriptio factor) It halts cell divisio whe DNA is damaged The either promotes repair of the DNA; or apoptosis (cell death) Mutatios i p53 are foud i 50% of all cacers

5 Cell Death Occurs i 2 ways: Necrosis: pathological chages kill a cell Apoptosis: ormal physiological respose Extrisic pathway ligads bid to death receptor proteis Itrisic pathway itracellular sigals Both pathways activate cytoplasmic caspases, which lead to cell death 3-58 : divisio of cells that results i daughter cells with oe-half of the geetic iformatio that the origial cell had Diploid 2 23 Haploid 23 Pa Haploid Ma Haploid Cell divisio occurrig i ovaries ad testes to produce gametes (ova ad sperm) Two divisioal sequeces Daughter cells have ½ the chromosomes the origial cell had Juior = Zygote = diploid orgaism=

6 I 1st divisio: homologous chromosomes pair alog equator of cell rather tha sigly as i mitosis 1 member of homolog pair is pulled to each pole gives each daughter cell 23 differet chromosomes, cosistig of 2 chromatids I 2d divisio: each daughter divides; chromosomes split ito 2 chromatids 1 goes to each ew daughter cell Each daughter cell cotais 23 chromosomes Orgial mother cell had 46 Aka reductio divisio Geetic diversity & I (first divisio) II (secod divisio) Geetic recombiatio occurs i prophase I 1. Crossig-over: Parts of oe homologous chromosome are exchaged with its parter homolog Early prophase I Chromati codeses to form visible chromosomes; each chromosome has 2 chromatids joied by a cetromere. Mid- to late prophase I Homologous chromosomes form pairs called tetrads. Chromatids ofte break ad exchage segmets (crossig-over). Cetrioles produce spidle fibers. Nuclear evelope disitegrates. Metaphase I Tetrads alig o equatorial plae of cell with cetromeres attached to spidle fibers. Chromosome Nucleus Cetromere Cetrioles Tetrad Crossig-over Spidle fibers Cetromere Chromatid Equatorial plae Prophase II Nuclear evelopes disitegrate agai; chromosomes still cosist of 2 chromatids. New spidle forms. Metaphase II Chromosomes alig o equatorial plae. Aaphase II Cetromeres divide; sister chromatids migrate to opposite poles of cell. Each chr omatid ow costitutes a sigle-straded chromosome. 2. Idepedet assortmet: the way chromosomes lie up durig metaphase is radom Aaphase I Homologous chromosomes separate ad migrate to opposite poles of the cell. Telophase I New uclear evelopes form aroud chromosomes; cell udergoes cytoplasmic divisio (cytokiesis). Each cell is ow haploid. Cleavage furrow Telophase II New uclear evelopes form aroud chromosomes; chromosomes ucoil ad become less visible; cytoplasm divides. Fial product is 4 haploid cells with sigle-straded chromosomes Please ote that due to differig operatig systems, some aimatios will ot appear util the presetatio is viewed i Presetatio Mode (Slide i the Normal or Slide Sorter views. All aimatios will appear after viewig i Presetatio Mode ad playig each aimatio. Most aimatios will require the latest versio of the Flash Player, Please ote that due to differig operatig systems, some aimatios will ot appear util the presetatio is viewed i Presetatio Mode (Slide i the Normal or Slide Sorter views. All aimatios will appear after viewig i Presetatio Mode ad playig each aimatio. Most aimatios will require the latest versio of the Flash Player, 6

7 Germ cells that migrate from yolk sac durig developmet become spermatogoia (stem cells) Spermatogoia replicate selves throughout life by mitosis Give rise to haploid sperm by meiosis Spermatogeesis Oogeesis 2 millio oocytes 400,00 oocytes 400 oocytes will ovulate Developmet of egg (oogeesis) Before birth I First polar body (dies) If ot fertilized 2 2 Multiplicatio of oogoia Primary oocyte Secodary oocyte Graulosa cells Bleedig ito atrum Ovulated oocyte Dies II Follicular fluid Secod polar body (dies) 2 Zygote Embryo Oocyte Nucleus Follicular cells Adolescece to meopause Graulosa cells Zoa pellucida Theca folliculi Atrum Cumulus oophorus Theca Secodary oocyte itera (ovulated) Theca If fertilized extera Developmet of follicle (folliculogeesis) Primordial follicle No chage Primary follicle Secodary follicle Tertiary follicle Ovulatio of mature (graafia) follicle Corpus luteum Epigeetic Iheritace Occurs whe gee silecig is passed o to daughter cells Gee silecig is eacted by DNA methylatio or posttraslatioal modificatio of histoes Ca cotribute to diseases Idetical twis ca have differeces i gee expressio --because of epigeetic chages i respose to differeces i their eviromets