Salivary gland- polytene chromosomes Brain-diploid metaphase chromosomes Same Objective Lens: Why are the salivary gland chromosomes so much larger? Alyssa.

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Salivary gland- polytene chromosomes Brain-diploid metaphase chromosomes Same Objective Lens: Why are the salivary gland chromosomes so much larger? Alyssa and Tyler

Fig MPF (Cdk/Cyclin Protein Complexes) Regulate Progression through Cell Cycle MPF= _________ (Cyclin- dependent Kinase) - regulates proteins by phosphorylation __________ - cell cycle phase- specific kinase regulators Cdk Cyclin SKIPPED in Polytene Tissues (Salivary Gland) How might cell cycle regulation differ ?

Chromatin: DNA Complexed with Protein 7x compaction 40x compaction 10,000x compaction Fig ,000x compaction Chromatin Packaging in Metaphase Chromosomes Chromatin Packaging in Salivary Gland Squash throughout cell cycle M phase only

7x compaction 40x compaction 10,000x compaction Fig ,000x compaction Dark Bands? Light Interbands? 30 nm fiber and higher Lower than 30 nm fiber Compaction Level heat shocked non-heat shocked

HP1 HP1 in transcriptionally silenced centromeric heterochromatin Which proteins would you expect to co-localize with HP1 here?

Fig HP1 binding to Me-K9 histone H3 to silence Transposable Elements in centromeric heterochromatin

Nucleosome - ~200 bp DNA wrapped around histone core octamer containing 2 each of 2 different heterodimers: histones - between (-) chgd. DNA backbone and (20-30% Lys/Arg) - highly conserved amino acid sequence - packing ratio 7:1 - -sites of covalent modifications Fig H2A/H2B and H3/H4 ionic bonds (+) chgd. histones N terminal tails

N-terminal Covalent Modifications Give a “Histone Code” Acetylation: Deacetylation: Methylation (, K20H4): Heterochromatin Fig Active Chromatin Inactive Chromatin K9H3, K27H3

7x compaction 40x compaction 10,000x compaction Fig ,000x compaction heat shocked non-heat shocked Acetylated Histones? De-acetylated Histones? Bands or Interbands? Interbands Bands

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