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BIOL 370 – Developmental Biology
Topic #10
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Amphibians and Fish: Early Development and
Axis Formation
Lange
Standardized Color Scheme:
Ectoderm – outer germ layer…
will become nervous system, tooth enamel, epidermis, lining of the mouth, anus,
nostrils, sweat glands, hair and nails.
Mesoderm – middle germ layer…
will become the muscle (smooth, cardiac and skeletal), connective tissues, dermis,
hypodermis (subcutaneous layer of the skin), bone, cartilage, red blood cells,
white blood cells, kidneys, and the adrenal cortex.
Endoderm – inner germ layer…
will become a variety of epithelia including the alimentary canal (excluding
specialized parts of the mouth, pharynx & rectum), the lining cells of all the glands,
trachea, bronchi, and alveoli of the lungs, endocrine glands, auditory tube, urinary
bladder and parts of the urethra.
Figure 7.23 Vegetal induction of mesoderm
Induction in this case is related to the activation of genes in the vegital
region that will guide development of the mesoderm.
Figure 7.23 Vegetal induction of mesoderm (Part 1)
Figure 7.23 Vegetal induction of mesoderm (Part 2)
Figure 7.25 The soluble protein Noggin dorsalizes the amphibian embryo
Figure 7.27 Model for the action of the organizer
Figure 7.29 Regional and temporal specificity of induction
Figure 7.30 Paracrine factor antagonists from the organizer are able to block specific paracrine
factors to distinguish head from tail
Bone morphogenetic
proteins (BMPs) are a
group of growth factors
also known as cytokines
and as metabologens.
Figure 7.30 Paracrine factor antagonists from the organizer are able to block specific paracrine
factors to distinguish head from tail (Part 1)
• BMPs were originally discovered through their ability to induce the
formation of bone and cartilage
• BMPs are now considered to constitute a group of pivotal
morphogenetic signals, orchestrating tissue architecture throughout
the body
Figure 7.30 Paracrine factor antagonists from the organizer are able to block specific paracrine
factors to distinguish head from tail (Part 2)
Figure 7.31 Cerberus mRNA injected into a single D4 blastomere of a 32-cell Xenopus embryo
induces head structures as well as a duplicated heart and liver
Figure 7.33 Insulin-like growth factors enhance anterior neural development
Figure 7.35 Model of organizer function and axis specification in the Xenopus gastrula
Figure 7.36 Pitx2 determines the direction of heart looping and gut coiling
Figure 7.37 Zebrafish development occurs very rapidly
Figure 7.37 Zebrafish development occurs very rapidly (Part 1)
Figure 7.37 Zebrafish development occurs very rapidly (Part 2)
Figure 7.38 Screening protocol for identifying mutations of zebrafish development
Figure 7.38 Screening protocol for identifying mutations of zebrafish development (Part 1)
Figure 7.38 Screening protocol for identifying mutations of zebrafish development (Part 2)
Figure 7.39 The gene for green fluorescent protein was fused to the regulatory region of a
zebrafish sonic hedgehog gene
Figure 7.40 Discoidal meroblastic cleavage in a zebrafish egg
Figure 7.41 Fish blastula
Figure 7.41 Fish blastula (Part 1)
Figure 7.41 Fish blastula (Part 2)
End.