Chapter 10.ppt-BB

65 negative 146 superhelical turns around the octamer

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Unformatted text preview: 5 negative 146 superhelical turns around the octamer superhelical Nucleosome Structure Revealed Nucleosome Markus Noll decided to test Kornberg’s model model - Digested DNA with the enzyme DNase I – Accurately measure the molecular weight of the resulting DNA Accurately fragments fragments The Hypothesis – The experiment tests the beads-on-a-string model of The chromatin structure If the model is correct, DNase I should cut in the linker If region region Interpreting the Data Interpreting 30 units ml-1 30 nm Fiber 30 Nucleosomes associate with each other to form a more compact Nucleosomes structure termed the 30 nm fiber 30 Histone H1 plays a role in this compaction – At moderate salt concentrations(100mMNaCl), H1 is removed The result is the – At low salt concentrations, H1 remains bound At The 30 nm fiber shortens the total length of DNA another s The _______-fold _______-fold - Two models have been proposed Further Compaction of the Chromosome The two events - shortened the DNA about 50-fold The A third level of compaction involves interaction third between the 30 nm fiber and the nuclear matrix nuclear involves the formation of involves _____________ _____________ Heterochromatin vs Euchromatin Heterochromatin vs The compaction level of interphase chromosomes is The not completely uniform not – Euchromatin – Heterochromatin Metaphase Chromosomes As cells enter M phase, the level of compaction As changes dramatically changes – By the end of prophase, sister chromatids are By entirely heterochromatic entirely These highly condensed metaphase These chromosomes undergo little gene transcription chromosomes Two multiprotein complexes help to form and organize Two metaphase chromosomes metaphase – Condensin Plays a critical role in Plays – Cohesin Plays a critical role in Plays Both contain a category of proteins called SMC proteins Both – Acronym = Structural maintenance of chromosomes Acronym tructural aintenance The condensation of a metaphase chromosome by condensin Cohesin at centromere is degraded Cohesin remains at centromere The alignment of sister chromatids via cohesin...
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This document was uploaded on 03/05/2014 for the course CELL 2050 at Tulane.

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