Name Student ID Page 1 Zoology 470 Exam 2 2014 This exam has 6 pages and a total of 50 points You will have 90 minutes to complete it Answer all short answer questions as briefly as possible Make sure your name and ID number are on all pages 1 3 points Provide concise definitions for each of the following a multicellular rosette b ectoderm c reductive cleavage 2 Egg activation is known to involve a number of ionic and signal transduction events a 2 points You treat a sea urchin egg with the BMS 354825 whioch inhibits the protein Src and then fertilize it What effects do you expect Explain your reasoning b 2 points You are testing a new inhibitor of Na H exchangers using sea urchin eggs What effects would this drug be expected to have on a fertilized sea urchin egg Explain your reasoning 3 Transcription factors can play a powerful role in sex determination a 2 points Sry is crucial for development of male mammals Describe one experiment that demonstrates that Sry is sufficient to confer the male phenotype Name Student ID Page 2 3 cont b 1 point Androgen insensitivity syndrome results from mutations in a hormone receptor which is required for cells to respond to testosterone Where is the primary site of action of this receptor once it has bound testosterone Primary site of action within the cell c 1 point Female mammals produce the sex hormone estrogen from another sex hormone What is this hormone Hormone 4 9 points Circle true T or false F for each of the following T F RNA helicases are a conserved component of germ plasm in many animal embryos T F T F Protein gradients as a patterning mechanism are possible in Drosophila because the early embryo is syncytial oskar would be expected to be a zygotically acting gene since it encodes a gene product required for germ cell formation in Drosophila embryos T F T F T F T F T F T F MicroRNAs are short RNAs that can regulate the translation of mRNAs T F T F T F T F Removing the RNA polymerase binding site from the even skipped gene would not be expected to disrupt the transcription of even skipped since its transcription is tightly controlled Removing the 3 untranslated region from the oskar RNA would be expected to affect where it is localized in the oocyte When the histones associated with a region of chromatin are heavily acetylated transcription of the associated gene would be more likely than when the histones are not acetylated Elongation of the archenteron in sea urchins occurs via convergent extension T F T F T T F F T F The expression of protein products from a gene can be regulated at the level of transcription or translation but not both Presumptive endodermal cells in C elegans are internalized via delamination Transcription factors can increase or decrease the amount of transcripts produced from the genes they regulate Anti M llerian hormone would be expected to be expressed at a higher level in a female mouse fetus than in a male mouse fetus Normal zebrafish primordial germ cells placed into an embryo lacking the function of the chemokine SDF 1 would be expected to migrate abnormally Sea urchins are thought to be more closely related to chordates than arthropods because they are deuterostomes Alternative splicing leads to the production of mRNAs with slightly different coding regions leading to proteins with slightly different amino acid sequence Ventral furrow formation during Drosophila gastrulation occur primarily by invagination Transplantation of primary mesenchyme cells from a normal embryo into an embryo whose dorsal ventral axis is perturbed would be expected to make a normal skeleton When primary mesenchyme cells ingress they would be expected to show in increase in cadherin based adhesion Name Student ID Page 3 5 Answer each of the following questions which relate to cleavage in early embryos a 1 point You observe a sea urchin zygote shown with RNA that encodes a fluorescent protein that acts as a reporter of Rho activity The zygote then goes on begin first cleavage as shown Assuming that the zygote on the left is drawn at a time immediately before the embryo on the right draw the region within the embryo on the left where you saw elevated Rho activity prior b 1 point What type of yolk distribution did the one celled zygote have that gave rise to the embryo at the right Type of yolk distribution c 2 points You work in Rick Elinson s lab at the University of Toronto You discover a frog species whose eggs have 1000 times as much yolk as the eggs of Xenopus laevis Before you look at a embryos of the new species Rick asks you to predict the likelihood of complete cleavage in the new species How would you repsond Explain your reasoning 6 2 points Germ plasm is a specialized type of cytoplasm found in many metazoans multicellular animals Describe one experiment that shows that germ plasm acts as a localized determinant that is sufficient for germ cell formation in Drosophila You need not describe detailed technical aspects of your experiment 7 Maternal polarity gene products dramatically affect anterior and posterior development in Drosophila Answer the following questions regarding how these proteins act Use the provided diagrams to indicate the expected expression of the molecule in each case a 1 point Indicate the expression pattern of caudal protein in an embryo derived from a bicoid loss of function mutant mother Anterior Posterior b 1 point Indicate the expression pattern of maternal hunchback mRNA in an embryo derived from a bicoid loss of function mutant mother Anterior Posterior Name Student ID Page 4 7 cont c 1 point Indicate the expression pattern of nanos mRNA when the anterior end of the oocyte is pricked with a needle and cytoplasm is allowed to ooze out Anterior Posterior d 1 point Indicate the pattern of zygotic hunchback mRNA expression in an embryo derived from a bicoid mutant mother Anterior Posterior 8 The following questions refer to genes that control segmentation in Drosophila 2 points a Certain mutations in the pair rule gene even skipped result in the loss of one or two specific stripes of even skipped expression in the embryo What defect s in the mutated evenskipped gene could account for this pattern of even skipped expression Explain your answer 1 point b Segment polarity genes are thought to be regulated heavily by the products of the pair rule genes What kinds of proteins are encoded by the pair rule genes Kind of protein 2 points c Armadillo the fly catenin is a segment polarity gene How