1. miRNA  miRNA ancient form of regulation.  Protection against viral pathogens  Quick regulation and turnover of mRNA.

2. Drosophila Development: Genetics at work!

3. Development of Drosophila

4. Closer look at Early Development of Drosophila.

5. Cellularization

6. Gastrulation and Segmentation

7. Anterior-Posterior Polarity in Oocyte  Starts during oogenesis  Gurken mRNA transferred to oocyte.  Signal sent back to oocyte post Gurken/Torpedo interaction.  Par-1 mediated organization of microtubules to posterior side of oocyte via Oskar. Minus end (posterior) and plus end (anterior).

8. Dorsal-Ventral Patterning in Oocyte.

9. Dorsal Gradient

10. Anterior-Posterior Polarity in Embryo

11. Syncytial Specification in Drosophila

12. Anterior-Posterior Polarity in Embryo

13. Translational Regulation  Stored oocyte mRNAs- selective inhibition of translation.  Genes turned on quickly post-fertilization.  Relies on the recruitment of proteins involved in making a polyA tail.  Drosophila Bicoid gene product.

14. Gap Genes  Role in early segmentation  Transcriptional regulators

15. Pair-rule Genes  Another set of Transcriptional Regulators.  Develops the precursors for the actual segments.  Zebra-stripe pattern of expression.  Stripe position determined by which enhancer is bound.

16. Pair-rule Genes

17. Segment Polarity Genes  Wingless (Wnt) and Hedgehog signal pathway proteins.  Paracrine signaling maintains segmentation.

18. Homeotic Selector Genes (Hox)  Regulated by Pair-rule and Gap genes.  Antennapedia Complex and bithorax complex.  AbdA and AbdB repressed by Hunchback and Kruppel.  Repression maintained by Polycomb, activation maintained by Trithorax.

19. Epigenetic Memory  Trithorax- keeps genes active.  Counteract Polycombs  Modify nucleosomes  Keep H3K4 trimethylated  Polycomb- keeps genes inactivated.  H3K27 methylase  Bind meH3 tails

20. Hox Genes in Other Species  Mouse Limb development- deletion of Hoxd11, Hoxd12, Hoxd13 causes polydactyly  Zebra fish, loss of H3K27 demethylase activity and subsequent Hox gene disregulation- poor tail development