Transcript Slide 1
Same Objective Lens: Salivary gland- polytene chromosomes Why are the salivary gland chromosomes so much larger? Alyssa and Tyler Brain-diploid metaphase chromosomes MPF (Cdk/Cyclin Protein Complexes) Regulate Progression through Cell Cycle SKIPPED in Polytene Tissues (Salivary Gland) MPF= Cdk _________ (Cyclindependent Kinase) - regulates proteins by phosphorylation Cyclin __________ - cell cycle phasespecific kinase regulators How might cell cycle regulation differ ? Fig. 14.8 7x compaction Chromatin Packaging in Salivary Gland Squash throughout cell cycle Chromatin: DNA Complexed with Protein 40x compaction Chromatin Packaging in Metaphase Chromosomes 10,000x10,000x compaction compactionFig. 12.12 M phase only 7x compaction non-heat shocked 40x compaction heat shocked Compaction Level Dark Bands? 30 nm fiber and higher Light Interbands? Lower than 30 nm fiber 10,000x10,000x compaction compactionFig. 12.12 Which proteins would you expect to co-localize with HP1 here? HP1 HP1 in transcriptionally silenced centromeric heterochromatin HP1 binding to Me-K9 histone H3 to silence Transposable Elements in centromeric heterochromatin Fig. 12.17 Nucleosome - ~200 bp DNA wrapped around histone core octamer containing 2 each of 2 different heterodimers: histones H2A/H2B and H3/H4 -ionic bonds between (-) chgd. DNA backbone and (+) chgd. histones (20-30% Lys/Arg) - highly conserved amino acid sequence - packing ratio 7:1 -N terminal tails-sites of covalent modifications Fig. 12.9 N-terminal Covalent Modifications Give a “Histone Code” Acetylation: Active Chromatin Deacetylation: Inactive Chromatin Methylation ( K9H3, K27H3 , K20H4): Heterochromatin Fig. 12.14 7x compaction non-heat shocked 40x compaction heat shocked Bands or Interbands? Acetylated Histones? De-acetylated Histones? Interbands Bands 10,000x10,000x compaction compactionFig. 12.12