Developmental Genetics in Drosophila Egg Polarity Establishment

1. MCDB 4650 Developmental Genetics in Drosophila

2. In the mature Drosophila egg before fertilization a) Neither the A-P nor the D-V polarity of the future embryo is yet established. b) The A-P polarity is established, but the D-V polarity must be established by sperm entry at fertilization. c) The D-V polarity is established, but the A-P polarity must be established by sperm entry at fertilization. d) Both the A-P and the D-V polarity of the future embryo are already established.

3. The nuclei in early fly embryos divide synchronously until cell cycle 14, when the syncytial blastoderm becomes cellularized and the embryo undergoes a midblastula transition (MBT), similar to that in the Xenopus embryo. Assume the mechanism for timing the MBT is the same as in Xenopus. If you artificially activate an unfertilized Drosophila egg to begin development (which is possible), when would you predict the MBT would occur? A) at cycle 13 B) at cycle 14 C) at cycle 15

4. You irradiate two different batches of embryos that are homozygous for a recessive cuticle color marker, yellow. The first batch is irradiated at cell cycle 15. The second batch is irradiated several cell cycles later. In some of the flies that develop from these embryos you find patches of yellow cells in the cuticle. Compared to the patches in the flies from later-irradiated embryos, the patches in the flies from earlier irradiated embryos will be A) smaller. B) larger.

5. Cells in columns 1 and 2 are heterozygous for the mutation in question. Cells in columns 3,4,5 are part of a clone homozygous for a bristle marker and a linked recessive Notch or Delta mutation. Which of the following results would indicate that the gene of interest acts non-cell autonomously ? a) Cells in columns 1 and 2 have a wild-type bristle phenotype. Cells in columns 3,4,5 have a mutant phenotype. b) Cells in columns 1, 2, and 3 have a wild-type bristle phenotype. Cells in columns 4 and 5 have a mutant phenotype. 1 2 3 4 5

6. What will be the phenotype of cells in columns 4, 5 and 6 if the gene acts non-cell autonomously and the arrangement of cells is as shown below? 1 2 3 4 5 6 a) All cells in columns 4, 5 and 6 will have a mutant phenotype b) All cells in columns 4, 5 and 6 will have a mutant phenotype except for the heterozygous cell (the white one) c) Some cells in columns 4, 5 and 6 will have a wild type phenotype; the heterozygous cell will have a mutant phenotype d) none of the above is correct

7. Based on the phenotypes exhibited by the four following classes of Drosophila embryonic lethal patterning mutants: pick the most likely normal function of the genes in that class from the numbered list of functions. (1) Establish the normal pattern of repeating segments. (2) Establish polarity of the D-V embryonic axis. (3) Establish the developmental identity of each embryonic segment. (4) Establish polarity of the A-P embryonic axis. (5) Establish positional identity of broad regions along the A-P axis. A. egg polarity genes B. gap genes C. dorsal genes D. pair rule genes

8. You have engineered a strain of Drosophila that produces 2x the normal amount of the bicoid gene product during oogenesis, and you have an antibody against the protein encoded by the gap gene Krppel that allows you to see where in the embryo this protein is expressed. In embryos from the bicoid over-expressing strain, would you predict that the expression domain of Krppel protein would be (1) more anterior, (2) more posterior, or (3) no different than its position in an embryo from a normal mother.

9. If a Drosophila bicoid/+ female is mated to a bicoid/+ male, which of the following is true? i) of the resulting embryos will develop normally. ii) of the resulting embryos will develop normally. iii) of the resulting embryos will develop normally. iv) All the embryos will develop normally.

10. If a bicoid/bicoid female is mated to a bicoid/+ male, i) of the resulting embryos will die. ii) of the resulting embryos will die. iii) All the resulting embryos will die. iv) The experiment cannot be done because viable bicoid/bicoid females cannot exist.

11. Which of the following questions could be answered using transgenic Drosophila? a. Which cells in the organism normally produce a particular transcript? b. What happens when a protein is expressed in a set of cells that do not normally express this protein? c. How does a gene product act in an embryo (does it work as a transcription factor, signaling molecule, etc?) d. a and b e. a and c f. b and c g. All of the above

12. If imaginal disc cells are determined to make one specific structure in the adult, what will happen if a set of cells is removed from one larva and placed into another larva in a different place ? a. The imaginal disc cells will not be able to differentiate b. The imaginal disc cells will differentiate into a structure dependent on where these cells were placed in the larva c. The imaginal disc cells will differentiate into the same structure they were supposed to make in the original fly d. The imaginal disc cells will differentiate into two different kinds of cells

13. You mate a wild type (+/+) male fly to a homozygous mutant bcd-/bcd- female fly. The bcd-/+ embryos from this mating will be: a) inviable, lacking anterior structures. b) inviable, lacking posterior structures. c) inviable, lacking anterior and posterior structures. d) wild-type, because the embryo is heterozygous

14. How is the positional identity of each cell established in the Drosophila embryo? a. signaling between individual cells b. segregation of either bicoid or nanos mRNA into individual cells c. diffusion of proteins that primarily act as transcription factors

15. Background: The germ line in Drosophila develops from the pole cells, which become cellularized and sequestered at the posterior tip of the embryo before the rest of the blastoderm cellularizes. Problem: Study the figure (9.37, included in the PowerPoint figures for Class 13) on the analysis of Drosophila torpedo in a germ line transplantation experiment. Based on the results shown, where must the torpedo gene normally be expressed for correct dorsal-ventral patterning? 1) in the oocyte, 2) in the follicle cells?