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DEVELOPMENTAL BIOLOGY
Wright Atlas – Chapter 1
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Chapter 1 – Atlas/Introduction
Developmental Biology The study of the formation of a new organism Development includes; Growth Differentiation Metamorphosis Tissue repair Regeneration Most organisms go through similar (general) stages of development during their life cycle
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Model Organisms It is unethical to experiment on human embryos
Must study model organisms to gain insights into human development No one single organism can give this These models include Plant (Arabidopsis thaliana) Fruit Fly (Drosophila melanogaster) Nematode (Caenorhabditis elegans) Zebra Fish (Brachydanio rerio) Frog (Xenopus tropicalis) Mouse (Mus musculus)
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Model Organisms Many model organisms are Dioecious
Exist as separate sexes Some exist are Sexually Dimorphic Sexes are distinguished externally Embryonic classification is made by examining the early formation of the gut Protostomes Mouth area opens first Deuterostomes Anus area opens first
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Protostomes and Deuterostomes
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Gastrulation and Formation of Blastopore
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Protostomes and Deuterostomes
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Phylogeny of the Model Organisms
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Mollusca Dioecious – exist as separate sexes One – distinctly female
Other – distinctly male Majority of animal species (some plants)
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Nematoda Adults live as males and self-fertilizing hermaphrodites (Ascaris is sexually dimorphic) Caenorhabditis elegans 3 days to mature
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Arthropoda Fertilization is internal and females lay up to 100 oocytes/day Drosophila melanogaster Dioecious and sexually dimorphic 6 days to full sexual maturity
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Drosophila Melanogaster
Excellent model to study Polytene chromosomes Arise in non-dividing cells Repeated DNA replication 100s of identical copies Identical banding patterns
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Echinodermata Classic embryology specimen - Echinoidea
Lytechinus pictus Excellent model to study fertilization Produces millions of gametes in one season Dioecious, but not sexually dimorphic
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Echinodermata Asteroidea Dioecious, but Not sexually dimorphic
Asterias Dioecious, but Not sexually dimorphic Seasonal spawning with transparent oocytes shed from ovaries Important in studying meiotic maturation
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Chordata Characteristics
Phylum Chordata Lancets, tunicates, vertebrates, …. Presences of Dorsal hollow nerve cord Notochord Pharyngeal slits Muscular postanal tail (at some time during embryonic development) Cephalochordata Front brain development Lancelet (branchiostoma)
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Chordata Characteristics
Pharyngeal slits Notochord Dorsal hollow nerve cord Postanal tail
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Diagram of Adult Lancet
Notochord Nerve cord Intestine Anus Pharyngeal slits Atriopore Gonads Buccal cirri
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Zebrafish Osteichthyes (Actinopterygii) Tropical freshwater fish
i.e. zebrafish (Brachydanio rerio) Release 100s of oocytes per day Develop rapidly ~3 days ; sexually mature ~3 months
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Amphibia Frogs and salamanders Large / robust embryos
Develop externally Easily undergo microsurgery Rana pipens & Xenopus laevis
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Aves Domestic chicken Gallus gallus & Gallus domesticus
Dioecious and sexually dimorphic Large & robust embryo Survive surgical manipulations
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Mammalia Most widely used is mouse model Mus musculus
Internal fertilization Oocytes easily undergo in vitro fertilization Develops asynchronously for about a week Sexual maturity in = 4 weeks Gestation 19 – 21 days Lives up to 3 years Transgenic Mice, Mouse knockouts, Genetically Engineered Mice
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Mammalia Used to teach mammalian embryology Domestic pig Sus scrofa
Makes anatomy easier to interpret from embryology
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Model Organisms
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Overview of Developmental Embryology Models
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Types of Cell Division
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Cell Cycle
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Fertilization
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Early Domains of Zygotic Genes
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Cleavage
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Classification of Morphogenetic processes
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Embryogenesis
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Axis of Symmetry
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Cortical Rotation
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Early Domains of Zygotic Genes
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Gastrulation
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Comparative Development of Mesoderm
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Neurulation
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Tailbud Stage
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Stages of Xenopus Development
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Xenopus Fate Mapping
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In Vitro Preparations of Sense mRNA or Antisense Hybridization
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Methods of Inhibition
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End of Wright Chapter 1
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