Questions in developmental biology. Differentiation Morphogenesis Growth/apoptosis Reproduction Evolution Environmental integration

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2 Questions in developmental biology Differentiation Morphogenesis Growth/apoptosis Reproduction Evolution Environmental integration

3 Representative cell types of a vertebrate zygote => embryo => adult differentiation vs. determination progressive recognition of cell types (markers)

4 Malpighi, 1672 Chick embryo development Lillie, 1902 Pander, 1817 Carlson, 1981

5 Early gastrula Fate mapping: tracing cell lineages

6 Tunicate Styela partita Pigmented cytoplasmic regions => follow

7 Remove B4.1 => no tail muscle

8 Vital dye marking

9 Fluorescent dye caged => laser activation Zebrafish embryo Labels diluted after cell divisions

10 Antibody to a quail-specific protein Genetic markers nucleolus

11 Transplantation Pigmented => unpigmented (donor) (recipient, host) To the same location Neural crest cell migration

12 Cut and Paste: basic strategy to study development Tissues Genes Mark cells to trace???

13 Rules of Evidence (cause-effect) Correlative (temporal order) Loss-of-function Gain-of-function find it; lose it; move it Biology, like any other science, does not deal with Facts, but with evidence.

14 Animal model Piebaldism sterility, anemia, unpigmented regions in skin, deafness, defect in gut neurons dominant mutation in kit affects proliferation and migration of neural crest cells, germ cell precursors, bloood cell precursors

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16 oocyte fertilization newly laid eggs Xenopus laevis

17 blastocoel Early blastula Late blastula

18 gastrulation Dorsal blastopore lip

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20 Chick embryo

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22 metamorphosis

23 Effect by environmental agents Thalidomide taken during pregnancy

24 Equiangular spiral growth

25 Allometric growth (different rates of growth)

26 Reaction-diffusion model

27 WT B-D: leopard mutants

28 Dictyostelium discoideum

29 camp

30 Cell adhesion molecules (CAM) gp24 induced after starvation gp80 streaming amoebae gp150 migrating slug

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32 camp is required for prespore formation WT prespore-specific marker + camp-degrading enzyme cellulose (stalk cell wall) + DIF inducing prestalk cells

33 Major evolutionary divergence

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37 Darwin: community of embryonic structures reveals community of descent barnacle crustacean, not mollusc shrimp Tunicate: larvae have notochords and formed neural tubes => chordate

38 Homologous structures (arise from common ancestral structure) Analogous structures (similar function, but not from a common ancestor) e.g bird wing and insect wing

39 Homologies of jaws and gill arches fish reptile mammal

40 Metazoans multicellular animals that pass through embryonic stages of development Diploblasts two germ layers (ectoderm, endoderm) Radiata: cnidarians, ctenophores radial symmetry Triploblasts three germ layers (ectoderm, endoderm, mesoderm) bilateral symmetry protostomes (mouth first, from blastopore) deuterostomes (mouth second; anus from blastopore)

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42 von Baer s principles 1. The general features of a large group of animals appear earlier in development than do the specialized features of a smaller group 2. Less general characters are developed from the more general, until finally the most specialized appear 3. The embryo of a given species, instead of passing through the adult stages of lower animals, departs more and more from them. 4. Therefore, the early embryos of a higher animal is never like the lower animal, but only like its early embryo.

43 Amniote egg originated in reptiles water => land Similar invention in arthropods

44 Pharyngeal (branchial, gill) arches Salamader embryo; surface ectoderm removed

45 Chick embryo

46 Acetabularia Nuclear control of morphogenesis

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48 Sexual reproduction in paramecium

49 Chlamydomonas

50 Meiosis

51 Volvocales Unicellular => multicellular species gonidia (germ cells)

52 Asexual reproduction in Volvox carteri 2 days cell movement resembling gastrulation

53 Bottle cells cell shape change => morphogenesis

54 somatic regenerator A blocked apoptosis somatic cells => gonidia

55 Sexual reproduction in Volvox carteri