Problem Set 1 Principles of Development Zoology 470 Spring 2015 20 Points Total Problem Set Guidelines 1 Due date This problem set is due by the end of class on Monday February 23 2015 2 Sources You may use any sources at your disposal to answer the following questions Legitimate sources include classmates knowledgeable friends and colleagues written documents and any other scientific resources you find useful If you work with other classmates on this problem set we ask that you list the other students with whom you worked to answer these questions Although you may discuss these questions as part of a group you are expected to answer the questions as an individual If you believe that published references will help you answer these questions you may cite those references However citation of additional references is not required nor is it expected 3 Answering the questions This problem set is designed to be answered concisely Brief but complete answers should be written in the space provided It is acceptable to type your answers but you must provide a hard copy of the document you generate Where you are asked for explanations you must provide them to receive full credit If you find it helpful feel free to include diagrams in your answers You need only turn in your answers on pages 2 3 Necessary information All of the information and techniques needed to answer the questions on p 2 3 have been presented in class or are to be found in Gilbert s Developmental Biology This problem set requires you to learn about mollusks whose development is described in Chapter 5 of Gilbert but other sections of Gilbert may be useful for some questions Although interesting due to time constrains we will not cover mollusks in class further Problem Statement Suppose that the 2011 T hoku earthquake and tsunami which caused the Fukushima Daiichi nuclear disaster resulted in the discovery of a new species of mud snail The adult snails look similar to the mud snail Ilyanassa obsoleta a small gastropod that lives in mud flats along the Atlantic coast A cursory examination of the embryos of the new species indicates that they have cell division patterns and produce polar lobes strikingly similar to those in Ilynassa embryos You travel to Japan to study the new species The questions on pp 2 3 deal with your research Zoo 470 2015 Problem Set 1 Page 2 Name Student Number If you worked in a group other collaborators 1 Classic concepts in developmental biology You perform classic embryology experiments to study how cells differentiate in the new species a The polar lobe produced in the one cell zygote of the new species is inherited by only one of the two cells in the 2 cell zygote You wish to show that as in other snails such as Ilynassa obsoleta cleavage of the zygote produces two daughter cells that are no longer totipotent Describe one experiment you could perform to demonstrate such lack of equivalence of the two cells in the zygote In your answer be sure to clearly state the expected outcome 4 points b The eyes in Ilynassa larvae are formed from micromeres i e from the group of small cells formed at the 8 cell stage You believe that eyes are formed by the identical cells in the new species Describe one experiment that would show that your belief is correct In your answer be sure to clearly state the expected outcome 3 points c Two micromeres called 1a and 1c give rise to cells that form eyes in Ilynassa Hyla Sweet then at the University of Texas showed in 1998 that one of the other micromeres 1b is also capable of forming eyes She believed that a macromere one of the large cells at the 8 cell stage called 1D induces 1a and 1c to form eyes normally but that 1b is normally too far away Design one experiment to test this hypothesis In your answer be sure to clearly state the expected outcome 4 points Zoo 470 2015 Problem Set 1 Page 3 2 Genetics and Developmental Biology Japanese scientists have isolated and maintained several mutant snails whose offspring appear to die at some high frequency but they have not carefully examine how many offspring die They believe that the radiation from the Fukushima nuclear plant caused these mutations a 1 point If the scientists hypothesis is correct the radiation is acting as what sort of agent Type of agent b You decide to investigate the nature of one of these mutations which you name mushi sushi m Because you have read about the famous maternal effect gene that controls snail shell coiling in other species your hypothesis is that mushi sushi acts as a maternal effect lethal gene Complete the following table which predicts the results from a cross between snails of various genotypes In your answer indicate the ratio of genotypes expected and the ratio of phenotypes expected 3 points m mushi sushi mutant allele normal allele Cross Genotype s of offspring and ratio of genotypes expected Percentage of dead offspring mm female x m male 3 Polar lobes may not contain the only important molecules passed on between cells in early snail embryos David Lambert working in Lisa Nagy s lab at the Univ of Arizona showed in 2002 that mRNA corresponding to the Ilynassa decapentaplegic dpp homologue i e a gene encoding a protein of the BMP family of growth factors associates with centrosomes in macromeres i e the large cells at the 8 cell stage Centrosomes are required for organizing microtubules correctly within eukaryotic cells After the macromeres form dpp mRNA is found at the cortex which lies just beneath the plasma membrane in early embryonic cells a You have cloned the dpp equivalent such related genes are called homologues in the new species and you are repeating some of Lambert s experiments Name one technique you could use to show where dpp mRNA localizes in 8 cell embryos of the new species 1 point Technique b The Nagy lab believes that dpp mRNA gets recruited to centrosomes by a dynein but that its later localization to the cortex depends on actin Describe one experiment you could perform to show that the localization of dpp mRNA to the cortex is actin dependent in the new species 3 points c The Nagy lab is developing techniques to knock down the function of gene products in snails They want to knock down the function of dpp but they do not want to disrupt dpp mRNA localization What technique would you recommend they use 1 point Technique