1. DEVELOPMENTAL BIOLOGY
Wright Atlas – Chapter 1

2. 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

4. 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)

5. 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

6. Protostomes and Deuterostomes

7. Gastrulation and Formation of Blastopore

8. Protostomes and Deuterostomes

9. Phylogeny of the Model Organisms

10. Mollusca Dioecious – exist as separate sexes One – distinctly female
Other – distinctly male
Majority of animal species (some plants)

11. Nematoda
Adults live as males and self-fertilizing hermaphrodites (Ascaris is sexually dimorphic)
Caenorhabditis elegans
3 days to mature

12. Arthropoda
Fertilization is internal and females lay up to 100 oocytes/day
Drosophila melanogaster
Dioecious and sexually dimorphic
6 days to full sexual maturity

13. Drosophila Melanogaster
Excellent model to study Polytene chromosomes
Arise in non-dividing cells
Repeated DNA replication
100s of identical copies
Identical banding patterns

14. Echinodermata Classic embryology specimen - Echinoidea
Lytechinus pictus
Excellent model to study fertilization
Produces millions of gametes in one season
Dioecious, but not sexually dimorphic

15. 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

16. 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)

17. Chordata Characteristics
Pharyngeal slits
Notochord
Dorsal hollow nerve cord
Postanal tail

18. Diagram of Adult Lancet
Notochord
Nerve cord
Intestine
Anus
Pharyngeal slits
Atriopore
Gonads
Buccal
cirri

19. 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

20. Amphibia Frogs and salamanders Large / robust embryos
Develop externally
Easily undergo microsurgery
Rana pipens & Xenopus laevis

21. Aves Domestic chicken Gallus gallus & Gallus domesticus
Dioecious and sexually dimorphic
Large & robust embryo
Survive surgical manipulations

22. 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

23. Mammalia Used to teach mammalian embryology Domestic pig Sus scrofa
Makes anatomy easier to interpret from embryology

24. Model Organisms

25. Overview of Developmental Embryology Models

26. Types of Cell Division

27. Cell Cycle

28. Fertilization

29. Early Domains of Zygotic Genes

30. Cleavage

31. Classification of Morphogenetic processes

32. Embryogenesis

33. Axis of Symmetry

34. Cortical Rotation

35. Early Domains of Zygotic Genes

36. Gastrulation

37. Comparative Development of Mesoderm

38. Neurulation

39. Tailbud Stage

40. Stages of Xenopus Development

41. Xenopus Fate Mapping

42. In Vitro Preparations of Sense mRNA or Antisense Hybridization

43. Methods of Inhibition

44. End of Wright Chapter 1