1. Chapter 9 - Axis specification in Drosophila Drosophila genetics is the groundwork for _______________l genetics Cheap, easy to breed and maintain Drosophila geneticists take pride in being __________, in ___________ information and being Mac users. Problems- fairly complex, non-transparent Fig. 8.1

2. Insects tend to undergo ________________- cleavage occurs at _____ of the egg In contrast to other creatures, insects form nuclei, then ____ ________ Fig. 9.1 Drosophila 1. Cleavage 17 10 Mitotic divisions #1-#9 - duplicate _____ (8 min/division) Mitotic division #10 – nuclei _______ to rim Termed a __________ _______ Mitotic division #11-14 – progressively _________divisions

3. Fig. 9.3 Drosophila 1. Cleavage 14 Mitotic divisions #14 – cells created with each nuclei to create the _______ _____________ Note – each nuclei has a _________ of cytoskeletal proteins Nuclei staun Tubulin stain Egg plasma membrane _____ between nuclei to create individual _____ Cycle 11-14- ______ ___________- nuclear division slows and __________ increases

4. 2. Gastrulation VentralDorsal Ventral furrow (from mesoderm) It becomes the ventral tube Segments 3 _____ 8 _________ Head Fig. 9.6 Fig. 9.7

5. 2. Gastrulation Establishment of anterior-posterior polarity- a. _______________- in specific region of egg b. _____-among 1 st gene transcribed in embryo c. ______ – result in 7 bands d. ____________ – result in 14 segments Gene family Fig. 9.8 Examples bicoid ____ caudel fushi tarazu ______ Kruppel _________ _______ wingless Protein gradients rule the day

6. 2. Gastrulation Active during creation of _________________ Fig. 9.10 _____ mRNA injected in anterior _______ mRNA injected, localize to posterior Hunchback (diffuse) Caudel (diffuse) Bicoid prevents ____ mRNA _____________ Nanos prevents_________ mRNA ___________ a. Maternal effect genes

7. Oocyte ________ Syncytial Blastoderm _______ Mechanism Anterior Posterior a. Maternal effect genes Fig. 9.11 ______ mRNA _____ mRNA Caudel and hunchback mRNA

8. What if we mess up the ______gradient? Bicoid - mutant Wild- type Two ____ Inject bicoid into: Anterior Wild-type Bicoid -/- MiddlePosterior _________ Head in ____ Two ____ Thus, bicoid specifies _______ development a. Maternal effect genes Fig. 9.14

9. How does nanos specify __________? Answer- By preventing _________ translation Anterior (no nanos) Mechanism In anterior, ________ binds 3’UTR (untranslated region) of hunchback mRNA, and mRNA is polyadenylated and translated In posterior, nanos prevents _____________, and thus prevents ____________ Posterior (with nanos) Fig. 9.16

10. 2. Gastrulation Segmentation genes Two steps in Drosophila development Bicoid, nanos, hunchback, caudel, etc. a.__________ ________ genes ____________ genes b. Gap genes c. ________ genes d. Segment polarity genes SpecificationDeterminationEgg (Cell fate is flexible)(Cell fate is determined) Maternal effect genes activate ____ genes, which activate _________ genes, which activate ________________ genes Segmentation genes establish ___________ GapPair-ruleSegment polarity Fig. 9.19

11. a. Gap Genes Gap genes respond to ________ _______ proteins Gap proteins interact to define specific________ of embryo Four major gap proteins- _______, ________, ________, _______ These are all _____________ proteins- activate or repress ______________ Fig. 9.21 Gap hunchback giant kruppel knirps

12. Fig. 9.21 b. Pair-rule genes Gap genes activate and repress ___________ genes in ________ stripe, resulting in ________ stripes Three major pair-rule proteins- ______, _____________, ______ These are all ____________ proteins- activate or repress transcription Cells in each ______________contains a unique ______ of pair rule genes expression unlike any other parasegment Pair-rule

13. Why do we observe expression of pair-rule proteins in ______________ segment? Answer- pair-rule genes use different ________ elements Example- even-skipped (a pair-rule gene) has several _______, but only one is _________ in a given stripe Fig. 9.22 This ________ is only active in stripe #1 b. Pair-rule genes Different concentrations of ____ proteins determine _________ gene expression

14. c. _________ __________ genes Pair-ruleSegment polarity Segment polarity genes act once cells are _______ _____________________ Maternal, gap and pair-rule genes operate ______ cells are formed 14 Fig. 9.1

15. c. Segment polarity genes Segment polarity genes encode proteins that make up ________ and __________ signal transduction pathways One cell produces ________ The adjacent cell produces ________ Wingless and hedgehog activate expression of _________ indirectly Fig. 9.25

16. 2. Gastrulation _______ _______ genes Responsible for directing structure formation of each segment These genes are clustered on chromosome 3 in the ________ ___________ (also called Hom-C) in two regions- The _______________ complex- The ________________ complex- Chromosome 3 1. The _____ of these genes on the chromosome matches order of ______________ expression 2. _____________ are regulated by all gene products expressed ___________ to it Two amazing features

17. What about ______________ polarity?? This occurs _______cells are created (post syncytial blastoderm) ______ ( a transcription factor) gradient is established Dorsal is found throughout syncytial blastoderm, but only in _______ of ______cells How does this occur? By a very complex pathway involving _____ and __________ proteins ( and a host of other proteins) Organs form at the ___________ of dorsal-ventral and ____________ regions of gene expression