Lecture 14 Gene Expression

Lecture 14 Gene Expression - ANNOUNCEMENTS Monday, March...

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ANNOUNCEMENTS – Monday, March 8th Final two lectures! Final Exam will be comprehensive; I’ve posted an old midterm from a previous year to provide a good idea of what to expect. Final Exam Review Session: Saturday, March 13 th from 5-7 PM in CENTER 115. Final Exam also here in CENTER 115, 7-10 PM, Monday March 15 th . Lecture 14 Eukaryotic Genome Regulation & Evolution http://www.youtube.com/watch? v=9k_oKK4Teco Many Levels of Eukaryotic Gene Regulation NUCLEUS CYTOPLASM CHROMATIN TRANSCRIPTION RNA PROCESSING RNA DEGRADATION Transport Translation PROTEIN PROCESSING DEGRADATION DNA RNA mRNA Protein Consequence of MIS -regulation: CANCER (Compare to bacterial Operon)
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“Junk DNA” in our genome Coding region (exons) (1.5%) Introns, promoters, enhancers (24%) Unique non- coding DNA (15%) Repetitive DNA (44%) More Repetiti ve DNA (15%) How would you organize your chromosomes in your nuclei? Eukaryotic Nucleus and Cell Animal Cell Nucleus 10 μ m Size of Eukaryotic (Human) Chromosomes One average human chromosome= 1.5 X 10 8 nucleotide base pairs, which is approximately 4 cm long, which is 40,000 Ж m 10 Ж m nucleus Try this with 46 chromosomes in one nucleus!!
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Nucleosomes: “Beads on a String” Unfolded chromatin: Each “bead” is a nucleosome , the basic unit of DNA packing 2 nm 10 nm DNA double helix Histones DNA “string” Nucleosome “bead” “Beads on a String” DNA Packing 1. Nucleosomes 10-nm nucleosomes , made of DNA and Histones Histone proteins bind tightly to DNA, throughout cell cycle Histones Linker DNA (“string”) Nucleosome (“bead”) 10 nm NUCLEOSOMES DNA Nucleosome 30 nm CHROMATIN FIBER 30-nm chromatin fiber made from packing of nucleosomes DNA Packing 2. Chromatin fiber 300-nm looped domains made from looping the 30-nm fiber, during prophase Protein scaffold 300 nm LOOPED DOMAINS Loops Scaffold DNA Packing 3. Looped Domains
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In mitosis , looped domains fold to form metaphase chromosome 700 nm 1,400 nm METAPHASE CHROMOSOME DNA Packing 4. Condensed Chromosomes Chromosome Coiling Movie Two chromosome states present in interphase cells 1. Euchromatin Highly extended and open state Most chromatin is in this state 2. Heterochromatin Highly condensed state Make “structural” parts of chromosome (centromere) Genome regions maintained in different chromatin states How Does Genome Structure…Relate to Genome Function? Sub-structures of chromatin Euchromatin (E) is more transcriptionally active because it’s more loosely packaged. Heterochromatin (H) is less transcriptionally active because it’s more tightly packaged.
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Differential Gene Expression A unique subset of genes is expressed in each cell type Organisms regulate which genes are expressed a time How does the presence of chromatin affect transcription (i.e. gene regulation)? Transcriptionally
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This note was uploaded on 03/31/2010 for the course BIOLOGY BILD 1 taught by Professor Traver during the Winter '10 term at UCSD.

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Lecture 14 Gene Expression - ANNOUNCEMENTS Monday, March...

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