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

2. Fig. 14.8 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 ?

3. Chromatin: DNA Complexed with Protein 7x compaction 40x compaction 10,000x compaction Fig. 12.12 10,000x compaction Chromatin Packaging in Metaphase Chromosomes Chromatin Packaging in Salivary Gland Squash throughout cell cycle M phase only

4. 7x compaction 40x compaction 10,000x compaction Fig. 12.12 10,000x compaction Dark Bands? Light Interbands? 30 nm fiber and higher Lower than 30 nm fiber Compaction Level heat shocked non-heat shocked

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

6. Fig. 12.17 HP1 binding to Me-K9 histone H3 to silence Transposable Elements in centromeric heterochromatin

7. 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. 12.9 H2A/H2B and H3/H4 ionic bonds (+) chgd. histones N terminal tails

8. N-terminal Covalent Modifications Give a “Histone Code” Acetylation: Deacetylation: Methylation (, K20H4): Heterochromatin Fig. 12.14 Active Chromatin Inactive Chromatin K9H3, K27H3

9. 7x compaction 40x compaction 10,000x compaction Fig. 12.12 10,000x compaction heat shocked non-heat shocked Acetylated Histones? De-acetylated Histones? Bands or Interbands? Interbands Bands