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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 A cell is an organism or a unit of a multi-cellular organism
4 Lecture 1Genetic Information and the Cell Nucleus
7 Several genomes of model system organisms have been sequenced Mouse! Zebrafish?
8 Mitochondria and chloroplasts contain their own genetic information 1.5 billion years ago
9 Many cell types, one genome: differentiation
The cells we have in our bodies are “wimpy” compared to protists 10
11 Karyotype Chromosome painting Different states of chromosomes throughout the life of a cell
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 Nucleosomes as seen in EM 30 nm thick Unfold into beads on a string DNA (string) and nucleosome core particles (beads)
15 The Zigzag model 30 nm fibers are often interrupted by sequence- specific DNA- binding proteins
20 Lampbrush chromosomes are interphase chromosomes in oocytes with active transcription Stiff extended chromatin loops
21 An RNA processing protein is shown green
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 Interphase chromosomes in insects-multiple cycles of DNA synthesis without cell division
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 Chromosome puffs 5 puffs 22 hours
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 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 Individual chromosomes occupy discrete territories in an interphase nucleus- not intertwined! By nuclear matrix or scaffold?
29 Chromosome regions that are close to nuclear envelope
30 Replication forks Helicase topoisomerase
31 Visualizing transcription (rRNA) RNA polymerase
32 Nucleolus is a ribosome-producing factory
33 txn assembly
34 Nucleoli dissociate and fuse
35 Fibrillarin (sno RNP) Pre-mRNA splicing Subnuclear structures: Nucleoli, Cajal bodies, GEMS, Interchromatin Granule clusters Or speckles, Chromatin
37 Ribosomes on ER
Dosage compensation 41 Barr body
42 Covalent modification of DNA
43 CpG islands--methylation inactivates transcription
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.