Ch 18 Developemental Genetics Study Guide Padilla
Ch 18 Developemental Genetics Study Guide Padilla biol 3452
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This 12 page Study Guide was uploaded by Jazmine Burnam on Sunday April 24, 2016. The Study Guide belongs to biol 3452 at University of North Texas taught by Melissa Lewallen in Spring 2016. Since its upload, it has received 90 views. For similar materials see Genetics Laboratory biol 3452 in Biology at University of North Texas.
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Date Created: 04/24/16
Study Guide- Developmental Genetics; Epigenetics Development: 1. Define the following: a. Differentiation: The process by which the cell achieves its final form and function b. c. Determination: A specific developmental fate of a cell becomes fixed. d. e. Specification: When genetic and positional cues confer a spatially discrete identity on cells. f. g. Zygote: cell that is formed when an egg and a sperm combine : a fertilized egg h. i. Syncytium: Mass of cytoplasm containing many nuclei enclosed by a single plasma membrane. j. Typically the result either of cell fusion or of a series of incomplete division cycles in which the nuclei divide but the cell does not. k. l. Imaginal Discs: group of undifferentiated cells in insect larva that develop into a specific adult structure m. n. o. p. q. Binary Switch Genes: genes that aact as switches, decreasing the number of alternative developmental pathways that a cell can follow Study Guide- Developmental Genetics; Epigenetics Decision point is binary (2 alternative developmental fates for a cell at a given time and the action of a switch gene programs the cell to follow only one of these pathways Defined by their ability to initiate complete development of an organ or a tissue type, and in combination with signaling pathways form GRNs (gene regulatory networks) r. s. Maternal Effect Genes: Genes in the maternal genome produce products (mRNA, protein) that are transferred to the egg t. Can be distributed in a gradient ~ 40 genes in flies u. v. Zygotic Genes: Genes transcribed after fertilization in the embryo. w. ~ 50-60 genes in flies x. y. Gap Genes: genes expressed in contiguous domains along the anterior- posterior axis of the drosophila embryo Regulate the process of segmentation in each domain z. aa. Homeotic Genes: encode transcription factors that control the expression of genes responsible for particular anatomical structures, such as wings, antennae ab. Homeotic selector genes specify parts of the adult body Study Guide- Developmental Genetics; Epigenetics Top= wildtype Bottom= Antp mutant ac. Pair-rule genes: Expression of Pair-Rule Genes: o the boundaries of segments o developmental fate of the cells. o encode transcription factors Mutations in Pair-Rule Genes eliminate segment size sections. ad. Segment Polarity Genes: Become active in a single band of cells around the embryo. Products control cellular identity within each segment. Embryo is divided into 14 segments. Some of the segment polarity gene products are transcription factors. ae. Invariant Lineage (in terms of development): A cell lineage is the developmental history of a differentiated cell as traced back to the cell from which it arises. Invariant patterns of cell division are in which specification of cell fates is correlated with cell division patterns. af. Programmed cell death/apoptosis: A genetically controlled program of cell death, activated as part of normal development or as a result of cell deat 2. What are the six terms used to describe the directionality/spatial characteristics of a developing organism (Hint: posterior is one of the terms). 1. Posterior (back) or Dorsal (lower) 2. Anterior (front) or Ventral (upper) 3. Superior (Cephalic toward the head) 4. Inferior (Caudal toward the tail) 5. Proximal (nearest to trunk) a. Used when referring to limbs 6. Distal (distant to trunk) a. Used when referring to limbs Study Guide- Developmental Genetics; Epigenetics 3. a .Describe the function of the eyeless gene and the phenotype for eyeless mutant. b. How was this gene discovered? c. What can occur if the eyeless gene is expressed in tissue that it normally is not expressed in? a. A switch gene which triggers the differentiation of the eye Eyeless gene is part of a network of genes that regulate eye development Master regulator of eye development Expressed in embryonic cells that become the eye Codes for a Transcription Factor b. Walter Gehring discovered the gene in 1994. Researchers ( Walter Gehring and his colleagues)made transgenic flies that carry copies of the mouse eyeless gene. Production of eye on wings, antennae, legs Study Guide- Developmental Genetics; Epigenetics Mouse gene works in flies! Pathway for eye development evolved long ago! c. If eyeless is expressed in other tissues such as legs, wings than an eye can be formed. Eyeless is able to direct the gene expression program for eye formation Eyeless is able to override the determination and differentiation programs in these tissues. 4. Describe the role in which macromolecule gradients within an embryo have in development. Bicoid forms a gradient across the anterior-posterior axis of the early Drosophila embryo that patterns the head and thorax forms in an embryonic syncytium consisting of a common cytoplasm supporting many nuclei 5. Describe the experiments conducted by Nusslein-Volhard and Wieschaus (who won the Noble Prize for their work using Drosophila) and their major findings/ideas in regards to embryo development. Experiments: Screened for genes that effect fly embryo development Looked for mutants that didn’t do their process o Classified mutants as normal embryo type or abnormal Major Findings/ideas in regards to embryo development: Identified many genes (60) that control development Identified and classified a small number of genes that are of key importance in determining the body plan and the formation of body segments Proposed a model that embryonic development is initiated by gradients of maternal effect gene products Study Guide- Developmental Genetics; Epigenetics 6. The field of developmental genetics relied on genetic techniques such as forward genetic screens and cell biology analysis/microscopy. Describe a study we discussed in class that used these techniques. Study of C. elegans lineage-identified cells that died (programmed ccell death) Programmed Cell Death/Apoptosis (Important for shaping of organs) o Chromosome condensation, Blebbing of plasma membrane, Cell death The genetic pathway that regulates apoptosis was first identified in C. elegans o 131 of 1090 cells in hermaphrodite die, 148 of 1179 in male o The point in development in which these cells die is always the same o All cells that undergo programmed cell death always use the same genetic pathway o In C. elegans ~15 genes are involved o Decision Makers o Execution of the decision o Engulfment of dying cells o Degradation of cell debris 7. Describe the phenotype associated with mutations in Runt/RUNX2 in various organisms. What is the function of these genes in various organisms? Function: Important gene controlling the initiation of bone formation in both mice and humans Runt: Mice homolog o Expressed early in development and controls formation of blood cells, bone, and the genital system o Mice with one mutant copy=similar to CCD in humans (see below) o Mice with two mutant copies= no bones at all (B) Contain only cartilage Study Guide- Developmental Genetics; Epigenetics Bone formation in wildtype mouse embryo (A) and Runx2 mutant mouse embryo (B). Cartlilage (blue) and bone (brown) is detected in wildtype but bone formation absent in mutant mouse. RUNX2: o Hole in top of skull due to bone does not form in the membranous gap (fontanel) o Collar bones (clavicles) do not develop Enabling affected individuals to fold their shoulders across their chest Human homolog of runt Causes CCD (cleidocranial dysplasia) o Autosomal dominant Phenotypes of CCD include Study Guide- Developmental Genetics; Epigenetics 8. How do cells signal neighboring cells? What are examples of such signaling pathways important for development? How cells signal Newly activated pathways act neighboring cells. both independently and in Cell-cell interactions influence coordinated networks to the transcriptional programs generate specific and developmental fate of the transcriptional patterns interacting cells and Signal networks establish surrounding cells anterior-posterior polarity and In early development animals body axes, coordinate pattern use a number of signaling formation, and direct the pathways to regulate differentiation of tissues and development; after organ organs. After organ formation begins, formation, additional pathways added to those already in use. Examples: Notch Pathway o Control developmental fate of interacting cell o Notch gene encodes a signal receptor protein embedded in the plasma membrane o Delta binds to notch protein, Cytoplasmic tail of the notch protein is cleaved off Binds to a cytoplasmic protein encoded by the SuH gene Moves to the nucleus where it activates a program of gene transcription Study Guide- Developmental Genetics; Epigenetics 9. Describe the contribution to developmental biology made by: Sydney Brenner, John Sulston and Robert Horvitz. What is the characteristics that distinguished C. elegans from other genetic model systems that helped with the study of development? Study Guide- Developmental Genetics; Epigenetics Contribution for their discoveries concerning "genetic regulation of organ development and programmed cell death" The Laureates have identified key genes regulating organ development and programmed cell death and have shown that corresponding genes exist in higher species, including man Sydney Brenner o Established C. elegans as a novel experimental model organism o provided a unique opportunity to link genetic analysis to cell division, differentiation and organ development – and to follow these processes under the microscope John Sulston o mapped a cell lineage where every cell division and differentiation could be followed in the development of a tissue in C. elegans o showed that specific cells undergo programmed cell death as an integral part of the normal differentiation process o Identified the first mutation of a gene participating in the cell death process. Robert Horvitz o discovered and characterized key genes controlling cell death in C. elegans o Showed how genes interact with each other in the cell death process and that corresponding genes exist in humans. Characteristics that distinguished C. elegans from other genetic model systems: its genetics are well known adults contain small # of cells genome is sequenced that follow highly deterministic lineage has been mapped fully develop from egg in 2 progra days 10. Define the cellular function for proteins encoded by ced-3, ced- 4, ced-9. What are the mammalian homologues for each? How were Study Guide- Developmental Genetics; Epigenetics the genes that regulate apoptosis identified? Why were these findings worthy of a Noble prize? Cellular function for proteins encoded by ced-3, ced-4, ced-9 functional ced-3 and ced-4 genes were a prerequisite for cell death to be executed ced-9, protects against cell death by interacting with ced-4 and ced-3 What are the mammalian homologues for each? More below Bcl2 (homolog for ced9) BAX (promotes apoptosis) blocks apoptosis Bcl2-BAX (inactive complex) How were the genes that regulate apoptosis identified? Forward genetic screen Why were these findings worthy of a Noble prize? Using the nematode C. elegans they demonstrated how organ development and programmed cell death are genetically regulated. They identified key genes regulating programmed cell death Demonstrated that corresponding genes exist also in higher animals, including man.
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