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UT Knoxville BIOL 240 - 2.williams_lecture.mitosis.meiosis

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PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Figure 2–1 A generalized animal cell.Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Slide 46Slide 47Slide 48Slide 49Fig. 1.19 Cytokinesis (cell division)Slide 51Slide 52Slide 53Slide 54Slide 55Slide 56Slide 57Slide 58Slide 59Biology 240 - General GeneticsSpring 2014Dr. Joe WilliamsContact: 974-6202, [email protected], January 13Unless otherwise indicated, photo credits are from:A.Klug WS, Cummings MR, Spencer CA, Palladino MA, Killian D. 2014. Concepts of Genetics. Boston: Pearson.B.Griffiths, S. Wessler, R. Lewontin, and S. Carroll. 2008. Introduction to Genetic Analysis, Eighth Edition. W. H. Freeman & Company.•Mastering Genetics – practice quizzes there – mult. Choice–Apparently it is only $7.50 extra to get this. RECOMMENDED–Problem with code? Use this code: MGENWILLIAMS81544If you are still having trouble getting into a discussion section,Please contact Randy Brewton•Email: [email protected]•Phone: (865) 974-6225•The UT office of undergraduate research is holding informational sessions to help students get started in pursuing undergraduate research. Please spread the word about this to any undergraduates who might be interested.•http://www.utk.edu/events/index.php?eID=57567Where are chromosomes located?Prokaryotes and viruses – haploid, one circular chromosomeuniparental inheritanceWhere are chromosomes located?Nucleus – diploid, linear chromosomes; biparental inheritancePlastids – haploid, circular, uniparental inherit. … prokaryote-likeFigure 2–1 A generalized animal cell.© 2015 Pearson Education, Inc.EukaryotesInheritance patterns depend on locations of genesCytoplasm = plastids or other DNA-containing elements:Cytoplasmic inheritance = genes inherited via chromosomes of plastidsUniparental inheritance pattern:Mitochondria usually inherited from your momChloroplasts usually inherited from maternal plantin Pine trees, chloroplasts are inherited from paternal plant8NNNNZygote/EmbryocpDNA, mtDNAonly from eggmaternally inheritedcytoplasmmtcpspermeggThe physical basis of inheritance(common pattern)NOmitochondrionchloroplastInheritance patterns depend on locations of genesCytoplasm = plastids or other DNA-containing elements:Cytoplasmic inheritance = genes inherited via chromosomes of plastidsuniparental inheritanceNucleus:Sex-linked inheritance = genes on sex-determining chromosomes are passed on differently than other genesAutosomal inheritance = genes on regular chromosomesGametes get only one sex chromosome – either X or YHumanMale½ of spermshave X½ of spermshave YGametes get all X chromosomesHumanFemale½ of spermshave one X½ of spermshave other X12Drosophila chromosomes1905 – Nettie Stevens names X chromosomein Tenebrio beetle, then in Drosophila131913 – Elinor Carothers experiment in grasshoppers showing independent assortment of chromosomes“Purple” chromosome moved to the same pole as the short-armed chromosome exactly half of the time.14Daughtercells areGametes =eggs or spermDaughtercellssister chromatidssister chromatids15MeiosisMitosis16Sexual reproductionCell divides leaving descendants that are not identical to parent(haploid, recombined)Begins with meiosis – diploid cells become reduced to haploid cells(recombination)Ends with fertilization (“syngamy”)Two haploid cells (egg and sperm) fuse to reform zygote, forming a diploid generation genetically different from parentAsexual reproductionCell divides to produce descendants identical to parentBegins and ends with mitosis - diploid cells produce diploid daughters (no recombination) “Somatic” cell lineage Zygote to mature organism17Major difference between mitosis and meiosisIn meiosis homologous chromosomes pair and “recombine”Each chromosome becomes a mosaic of the two homologous parent chromosomesBecause of recombination, genes that are physically on the same chromosome are still often inherited according to Mendel’s law of independent inheritance – as if they were separate “particles”Recombination is the hallmark of meiosis, and of sexual reproduction18The cell cycleInterphase19The cell cycle20S-phase: DNA synthesis2n 4nG1-phase: “gap 1” = growth and biosynthesis2n G2-phase: “gap 2” = growth and prep for mitosis4n MitosisMeiosisG0-phase (arrest)21The cell cycleInterphase22MitosisMeiosisGametes1n23S-phase: DNA synthesis2n 4nG1-phase: “gap 1” = growth and biosynthesis2n G2-phase: “gap 2” = growth and prep for mitosis/meiosis4n MitosisMeiosisG0-phase (arrest)24•How is the cell cycle regulated?•Passage from one stage to another is controlled by cyclins, proteins that regulate cell growth and division25The cell cycle proceeds via checkpointsMost terminally-differentiated cells stay in G0/1G1/S checkpointG2/M checkpointM checkpoint26G1 (Gap 1)-phasea. Microtubules reassembleb. Cell enlargesc. Organelles (plastids) duplicated. Differentiated cells are arrested in G1 (=G0) but dividing cells can be in G1 for only a short timeINTERPHASEINTERPHASE27S (synthesis)-phase - DNA duplication occursa. Each chromosome duplicates to form two identical chromatids b. Chromatids are connected at the centromereINTERPHASEINTERPHASEchromatidchromosomechromosomeDuplicated Chromosomes are held together at centromereSister chromatids identicalDon’t confuse duplicated chromosomes withhomologous chromosomesSister chromatids identicalHomologous chromosomes nearly identicalHomologous chromosomesEg. “Chromosome 5”5A and 5B30G2 (Gap 2)-phase a. Newly replicated chromatin begins to condenseb. Tubulin is synthesized which will make microtubulesc. 3-5 hours longINTERPHASEINTERPHASE31In late G2 chromosomes begin to “condense”The first stage occurs when a DNA strand wraps around a complex of proteins (histone proteins) known as a nucleosomeNucleosome32Electron microscope photos of DNA complexed with nucleosomes33Prophase chromosomeChromosomes are only condensed (and easily visualized) near the time of mitosisMetaphase chromosomes35Pollen germinationActive nucleus (uncoiled DNA)sperm DNA(highly condensed)Pollen grain36MitosisMitosis37MITOSIS IN ONION ROOT TIP CELLS38“PMAT”1A1B1A1B39•Chromatids


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