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miRNA miRNA ancient form
of regulation. Protection against
viral pathogens Quick regulation and
turnover of mRNA.
Drosophila Development: Genetics at work!
Development of Drosophila
Closer look at Early Development of Drosophila.
Cellularization
Gastrulation and Segmentation
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).
Dorsal-Ventral Patterning in Oocyte.
Dorsal Gradient
Anterior-Posterior Polarity in Embryo
Syncytial Specification in Drosophila
Anterior-Posterior Polarity in Embryo
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.
Gap Genes Role in early
segmentation Transcriptional
regulators
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.
Pair-rule Genes
Segment Polarity Genes Wingless (Wnt) and
Hedgehog signal pathway proteins.
Paracrine signaling maintains segmentation.
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.
Epigenetic Memory Trithorax- keeps genes active.
Counteract Polycombs Modify nucleosomes Keep H3K4 trimethylated
Polycomb- keeps genes inactivated. H3K27 methylase Bind meH3 tails
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