ex2_2008_key - Name: _ Student ID:_ Page 1 Zoology 470 -...

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Name: ______________________________________ Student ID:________________________ Page 1 Zoology 470 - Exam #2 – 2008 This exam has 5 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. You will receive 1 point for doing so. 1. Provide concise definitions for each of the following ( 5 points ) a. Wolffian duct: Tubular structure that is retained in male mammals. It becomes portions of the male reproductive tract, including the vas deferens. b. midblastula transition: Transition that occurs at different times in different organisms, but is accompanied by randomization of cell division, and a large-scale transition from reliance on maternal transcripts to production of zygotic transcripts. c. ectoderm: Most external of the three primary germ layers. Ectodermal fives rise to tissues such as epidermis and neural tissues. d. contractile ring: Actomyosin-based structure that is responsible for pinching daughter cells off during cytokinesis. The CR is found at the cleavage furrow. e. invagination: Inward bending of sheet of tissue . 2. Complete the following table referring to cleavage patterns in early embryos of various animals ( 4 points ) Animal Yolk Distribution Completeness of Cleavage Orientation of cleavages Squid (cephalod mollusk) telolecithal meroblastic bilateral Chimpanzee (mammal) isolecithal holoblastic rotational Earthworm (annelid) isolecithal holoblastic spiral Salamander (amphibian) mesolecithal holoblastic radial 3. Transcription factors can play a powerful role in the differentiation of tissues in embryos. a. The pax-6 family of proteins are important for the development of eye structures. Describe one experiment that demonstrates a pax-6 family member is necessary for eye development ( 2 points ): eyeless mutants in flies, small eye mutants in mice, and aniridia patients in humans all carry mutations in the pax-6 equivalent. [Note: overexpression does NOT prove necessity, but merely sufficiency] b. Sry is crucial for development of male mammals. Describe one experiment that demonstrates that Sry is sufficient to confer the male phenotype ( 2 points ): Transgenic mice carrying an sry transgene who are XX display male characteristics; XX mice with a crossover that carries the sry locus onto the pseudoautosomal region of one X chromosome have the same phenotype.
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Name: ______________________________________ Student ID:________________________ Page 2 4. Circle true (T) or false (F) for each of the following ( 7 points ) T RNA helicases are a conserved component of germ plasm in many animal embryos T Protein gradients as a patterning mechanism are possible in Drosophila because the early embryo is syncytial F oskar would be expected to be a zygotically acting gene, since it encodes a gene product required for germ cell formation in Drosophila embryos [maternally acting] F Genes can be transcriptionally regulated or translationally regulated, but not both
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This note was uploaded on 08/08/2008 for the course ZOO 470 taught by Professor Hardin during the Spring '08 term at Wisconsin.

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ex2_2008_key - Name: _ Student ID:_ Page 1 Zoology 470 -...

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