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  1. 1 http://www.biology.ucsd/classes/bicd110.SP07/ Works for everyone? Office hr:5-6 Thr Office hr:10-11am Wed ROMA cafe Office hr:5-6 Thr Geisel S&E

  2. 2 A cell is an organism or a unit of a multi-cellular organism

  3. 3

  4. 4 Lecture 1Genetic Information and the Cell Nucleus

  5. 5

  6. 6

  7. 7 Several genomes of model system organisms have been sequenced Mouse! Zebrafish?

  8. 8 Mitochondria and chloroplasts contain their own genetic information 1.5 billion years ago

  9. 9 Many cell types, one genome: differentiation

  10. The cells we have in our bodies are “wimpy” compared to protists 10

  11. 11 Karyotype Chromosome painting Different states of chromosomes throughout the life of a cell

  12. 12 Three DNA sequences required to produce a Chromosome: 1. 2 Telomeres (replication and prevent sticking) 2. Centromere (Kinetochore) (attaching daughter chromosomes) 3. 2 replication origins

  13. 13 Nucleosomes as seen in EM 30 nm thick Unfold into beads on a string DNA (string) and nucleosome core particles (beads)

  14. 14

  15. 15 The Zigzag model 30 nm fibers are often interrupted by sequence- specific DNA- binding proteins

  16. 16

  17. 17

  18. Covalent modification of core histone tails 18

  19. 19

  20. 20 Lampbrush chromosomes are interphase chromosomes in oocytes with active transcription Stiff extended chromatin loops

  21. 21 An RNA processing protein is shown green

  22. 22 DNA from organisms that usually do not produce lampbrush chromosome is packaged into lampbrush chromosomes-- maybe all are in loop forms but are smaller Actively expressed Not expressed

  23. 23 Interphase chromosomes in insects-multiple cycles of DNA synthesis without cell division

  24. 24 Bands (95%) and interbands (5%). Both have genes. Bands do not correlate with genes. Some bands have multiple genes and some lack genes Three times more genes than Bands Different levels of gene expression: Higher at interbands. Heterogeneity of chromosomes (dynamic)

  25. 25 Chromosome puffs 5 puffs 22 hours

  26. 26 RNA synthesis in chromosome puffs Polytene chromosomes from C. tentans New RNA in red 3H-uridine Older RNA in blue BrUTP Autoradiograph EM

  27. 27 Heterochromatin--no expression 10%, additional levels of packing of 30-nm fibers. Commonly found around centromeres, near telomeres, other positions. Not “dead” DNA but has important functions; Euchromatin-- interphase chromosomes, looped 30-nm Fibers.

  28. 28 Individual chromosomes occupy discrete territories in an interphase nucleus- not intertwined! By nuclear matrix or scaffold?

  29. 29 Chromosome regions that are close to nuclear envelope

  30. 30 Replication forks Helicase topoisomerase

  31. 31 Visualizing transcription (rRNA) RNA polymerase

  32. 32 Nucleolus is a ribosome-producing factory

  33. 33 txn assembly

  34. 34 Nucleoli dissociate and fuse

  35. 35 Fibrillarin (sno RNP) Pre-mRNA splicing Subnuclear structures: Nucleoli, Cajal bodies, GEMS, Interchromatin Granule clusters Or speckles, Chromatin

  36. 35

  37. 37 Ribosomes on ER

  38. 38

  39. 39

  40. 40

  41. Dosage compensation 41 Barr body

  42. 42 Covalent modification of DNA

  43. 43 CpG islands--methylation inactivates transcription

  44. 44 Summary Eukaryotic cells keep genetic information in DNA enclosed in cell nucleus and mitochondria and chloroplasts (plants); The genomes of several model organisms are completely sequenced; 3. Long DNA molecules are efficiently packed in chromosomes; Cell nucleus is a highly organized structure; Different sets of genes are expressed in different tissues; Epigenetic regulation of gene expression.