prelim 2 - and this generally is not transcribed, in...

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Chapter 19: Eukaryotic Genomes 1. In eukaryotes, the dna protein complex, called chromatin, is ordered into higher structural levels than the dna-protein complex in prokaryotes. 2. In interphase, the chromatin usually appears as a diffuse mass within the nucleus, suggesting that the chromatin is high extended. 3. Proteins called histones are responsible for the first level of dna packing in chromatin. The mass of histone in chromatin is approximately the mass of dna 4. Histones are positive and bind to the negative dna 5. Appears as “beads on a string” 6. Each “bead” is a nucleosome, and each nucleosome has 2 molecules of 4 different types of histones 7. With the aid of histone1 (H1), the interactions between histone tails to coil and fold. 8. During prophase, further folding of the fiber into looped domains. The loops are attached to a protein scaffold of nonhistone proteins. 9. There is futher folding and condensing in metaphase 10. In interphase you can get heterochromatin, which is inaccessible to transcription enzymes
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Unformatted text preview: and this generally is not transcribed, in contrast to euchromatin which is loosely packed and is more accessible to enzymes so transcription can occur. 11. A typical human cell expresses only 20% of it’s genes at a given time 12. The differences between cell types, therefore are due not to different genes being present, but to differential gene expression, the expression of different genes by cells with the same genome. 13. Stages in gene expression that can be regulated in eukaryotic cells a. chromatin modification, dna unpacking involving histone acetylation and dna demethylation b. gene available for transcription c. transcription occurs d. then you have a primary transcript, with exons and introns still e. rna processing, which cuts out the introns f. mRna in nucleus g. which gets transported to cytoplasm h. translation occurs and degradation of mRna i. polypeptide, j. cleavage chemical modification, transport to cellular destination k. active protein l. degraded protein 14....
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This note was uploaded on 09/09/2011 for the course BIO 102 taught by Professor Staff during the Spring '08 term at SUNY Buffalo.

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