The DNA ladderingDNA was fragmented into-180 bpduring apoptosis by the caspaseassay of apoptosis:activated DNase(CAD)ApoptosisWhitetloodceApoptosis2342000bpCetis thatundergo apoptosis1500bpApoptoticcelare enguifedbya type of whitebiood cell calledamacrophage1000bp750bphistone octameric core"heads on a string fortn(2xH2A,H2B,H3andHA)of chromatin"500bpmdceaseQ0senave250bp200bp13-16
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 13-16 DNA was fragmented into DNA was fragmented into ~180 bp during apoptosis by the during apoptosis by the caspase caspaseactivated activated DNase (CAD). The DNA laddering assay of apoptosis: Apoptosis
Spacing and structure of nucleosomes affects gene expressionDNA in the regions between nucleosomes is availablefor interactionswith proteins involved in expression, regulation, and furthercompaction.The way in which DNA is wound around a nucleosome plays a role indetermining how certain proteins interact with specific DNA sequences.Packaging into nucleosomes condensesDNA 7-fold2metersofDNAshortenstolessthan0.25meters13-17
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 13-17 Spacing and structure of Spacing and structure of nucleosomes nucleosomes affects affects gene expression gene expression. DNA in the regions between DNA in the regions between nucleosomes nucleosomes is available for interactions is available for interactions with proteins involved in exp with proteins involved in expression, regulation, and further ression, regulation, and further compaction. compaction. The way in which DNA is wound around a The way in which DNA is wound around a nucleosome nucleosome plays a role in plays a role in determining how certain proteins determining how certain proteins interact with specific DNA sequ interact with specific DNA sequences. Packaging into Packaging into nucleosomes nucleosomes condenses DNA condenses DNA 7-fold. 2 meters of DNA shortens to less than 0.25 meters. 2 meters of DNA shortens to less than 0.25 meters
Models of higherlevel compaction seek to explain extremecompactionofchromosomesFormation of3o0 Afiber through supercoilinga20Aindiameter100A100Afiber300Afiber300A(superhelix)Fig.11.513-18
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 13-18 Models of higher level compaction seek to explain extreme Models of higher level compaction seek to explain extreme compaction of chromosomes compaction of chromosomes Formation of 300 Formation of 300 Å fiber through fiber through supercoiling supercoiling Fig. 11.5
Radial loop-scaffold modelfor higherlevels of compactionEach loop contains60-100kbofDNANonhistonescaffoldproteinstethered by(b)nonhistonescaffoldproteins.NonscaffoldproteinLoopchromatinFig.11.513-19
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 13-19 Each loop contains Each loop contains 60-100 kb of DNA 100 kb of DNA tethered by tethered by nonhistone nonhistone scaffold scaffold proteins. proteins. Fig. 11.5 Radial loop Radial loop-scaffold model scaffold model for higher levels of compaction for higher levels of compaction
InterphasecMetaphasechromosomechromatinRosettescompressedintoacompactbundleAdditionalnonhistonescaffoldcomponentsFig.11.513-20
Fig. 11.5 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 13-20