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Developmental Biology - PowerPoint PPT Presentation

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An Understanding of Everything. Developmental Biology. Stages & Events of Chordate Embryogenesis. Developmental Process. Embryonic Stage. Zygote . Morula. Blastula. Gastrula. Neurulation. Neurula. Pharyngula. Fetus. Gametogenesis. Process of producing gametes Spermatogenesis

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stages events of chordate embryogenesis
Stages & Events of Chordate Embryogenesis

Developmental Process

Embryonic Stage









  • Process of producing gametes
    • Spermatogenesis
    • Oogenesis
  • Meiotic cell division
  • Packaging of material into oocytes
  • Removal of cytoplasm from sperm
localization of developmental regulatory factors
Localization of Developmental Regulatory Factors
  • Dsh, Xcat-2, Xlsirt, Vg-1 mRNAs localized to vegetal pole of vertebrate eggs

Xlsirt mRNA

fertilization induces a rearrangement of cytoplasmic localized factors
Fertilization Induces a Rearrangement of Cytoplasmic, Localized Factors
  • Initial localization of material in eggs is radially symmetrical
  • Fertilization creates a point of asymmetry and causes rotational reorganization of cytoskeleton to generate bilateral symmetry

Gray crescent

concepts in developmental biology
Concepts in Developmental Biology
  • Polarity
    • Established by localization of maternal gene products
    • Established by inductive signaling events
  • Morphogenesis
    • Cellular movements and embryonic structure formation
    • Regulated by cell-signaling & cell adhesion mechanisms
  • Differentiation
    • Specialization of cells to a particular fate
  • Growth
    • Increase in cell number
    • Increase in cell size
cell specification
Cell Specification
  • Differentiation
    • The process and the processes associated with a cell becoming specialized
    • Occurs in multiple steps
cell specification1
Cell Specification
  • Autonomous
    • All differentiation information is contained within the cell
  • Conditional
    • Differentiation information supplied through interactions with other cells
cell specification steps
Cell Specification - Steps
  • Commitment
    • Specification
    • Determination
  • Terminal differentiation
cell specification commitment
Cell Specification - Commitment
  • Specification
    • A cell is said to be specified when:
    • Cells differentiate autonomously when removed from normal environment (embryo) and placed in a neutral environment (culture medium)
    • Placing cells into a non-neutral environment (a different place in the embryo) causes the cells to follow the fate of other cells the new location rather than their original fate
cell specification committment
Cell Specification - Committment
  • Determination
    • A cell is said to be determined when:
    • Cells differentiate autonomously even when placed in a non-neutral environment
    • When moved to a different location within the embryo, the transplanted cells differentiate according to their original fate
cell specification terminal differentiation
Cell Specification - Terminal Differentiation
  • When a cell can no longer change or be changed into anything other than the cell type it is
  • Can be associated with permanent changes in DNA
    • DNA Methylation is a prominent factor
    • B-cells (plasma cells) rearrange the immunoglobulin (Ig) genes so that they can now only form a single type of Ig
spemann s specification experiments
Spemann’s Specification Experiments

Inductive signals trigger conditional specification, determination and differentiation

Presumptive neural plate ectoderm in the early gastrula was uncommitted. Later gastrula neuroectoderm was committed to a neural fate.

reversal of terminal differentiation
Reversal of Terminal Differentiation
  • Embryonic Stem cells
    • Totipotent or pluripotent cells
  • Dedifferentiated stem cells
    • Pluripotent
    • Derived from previously differentiated cells
  • Cloning proves nuclear equivalence
cloning by nuclear transplantation
Cloning by Nuclear Transplantation
  • Nuclear transplant experiments have shown that somatic cells contain the entire genome.
  • Nucleus of an unfertilized egg is replaced with the nucleus of a somatic cell
  • These experiments led to two important conclusions:
    • No information is lost in the early stages of embryonic development (a principle known as genomic equivalence).
    • The cytoplasmic environment around a nucleus can modify its fate.
the first cloning experiment nuclear transplantation in xenopus laevis
The First Cloning Experiment – Nuclear Transplantation in Xenopus laevis

Cloning of the frog Xenopus laevis by nuclear transplantation of albino gut cell nuclei into enucleated, wt oocytes. All progeny are albino & female




a gene cascade controls pattern formation in the drosophila embryo
A Gene Cascade Controls Pattern Formation in the Drosophila Embryo

Maternal effect genes

Gap genes

Pair rule genes

Segment polarity genes

Homeotic genes

northern analysis gel
Northern Analysis: Gel


Formaldehyde gels

Methyl-mercury-OH gels

northern analysis probing
Northern Analysis: Probing

Spatial expression information

rna localization developmental stages
RNA LocalizationDevelopmental Stages

temporal expression information