6.Experiments with Xenopus (frog) in the late 1950s demonstrated that cells within the 3 germ layers had an affinity for each other and thus indicated that they had differentiated enough to be “biased” toward a specific cell layer (endoderm, mesoderm, ectoderm). Describe an experiment that demonstrated how the 3 different layers of the gastrula have an affinity for each other. 7.Morphogenesis involves the orchestration of Cell Affinity, Cell Adhesion, and Cell Migration. How do the adhesive molecules play a role as cells of the embryo change their affinity for one another? PLEASE ANSWER BOTH QUESTIONS Solution 1. Taking an advantage of discovery of amphibian tissues become dissociated into single cells when placed in alkaline solupans, 2. The prepared single-cell suspensions from each of three germ layers of amphibian embryos soon after the neural tube had formed. 3. Take two or more of these single-cell suspensions could be combined in various ways. When the pH of the solution was normalized, the cells adhered to one another, forming aggregates on agar-coated petri dishes. 4. This experiment shows affinity of 3 different layers of the gastrula. Cell Affinity: a) The inner surface of the ectoderm has a positive affinity for mesodermal cells and a negative affinity for the endoderm. b) While the mesoderm has positive affinities for both ectodermal and endodermal cells. c) Mimicry of normal embryonic structure by cell aggregates is also seen in the recombination of epidermis and neural plate cells. Cell Adhesion: a) cadherins are calcium-dependent adhesion molecules. They are critical for establishing and maintaining intercellular connections, and they appear to be crucial to the spatial segregation of cell types and to the organization of animal form. b) The cadherins are anchored inside the cell by a complex of proteins called catenins and the cadherin-catenin complex forms the classic adherens junctions that help hold epithelial cells together. Cell Migration: a) migration involves the adhesion of the cell to its extracellular substrate. The moving cell needs something to push on, and attaches to the surrounding matrix. b) Integrins span the cell membrane, connecting the extracellular matrix outside the cell to the actin cytoskeleton on the inside of the cell. These connections of actin to integrin form focal adhesions on the cell membrane where the membrane contacts the extracellular matrix. c) Myosin and its regulators provide the motive force along these actin microfilaments.they are linked with the lamellipodial actin at the sites of adhesion. d) Release of adhesions in the rear, allowing the cell to migrate in the forward direction. It is probable that stretch-sensitive calcium channels are opened and that the released calcium ions activate proteases that destroy the focal adhesion sites..

1. 6.Experiments with Xenopus (frog) in the late 1950s demonstrated that cells within the 3 germ
layers had an affinity for each other and thus indicated that they had differentiated enough to be
“biased” toward a specific cell layer (endoderm, mesoderm, ectoderm). Describe an experiment
that demonstrated how the 3 different layers of the gastrula have an affinity for each other.
7.Morphogenesis involves the orchestration of Cell Affinity, Cell Adhesion, and Cell Migration.
How do the adhesive molecules play a role as cells of the embryo change their affinity for one
another?
PLEASE ANSWER BOTH QUESTIONS
Solution
1. Taking an advantage of discovery of amphibian tissues become dissociated into single cells
when placed in alkaline solupans,
2. The prepared single-cell suspensions from each of three germ layers of amphibian embryos
soon after the neural tube had formed.
3. Take two or more of these single-cell suspensions could be combined in various ways. When
the pH of the solution was normalized, the cells adhered to one another, forming aggregates on
agar-coated petri dishes.
4. This experiment shows affinity of 3 different layers of the gastrula.
Cell Affinity: a) The inner surface of the ectoderm has a positive affinity for mesodermal cells
and a negative affinity for the endoderm.
b) While the mesoderm has positive affinities for both ectodermal and endodermal cells.
c) Mimicry of normal embryonic structure by cell aggregates is also seen in the recombination of
epidermis and neural plate cells.
Cell Adhesion: a) cadherins are calcium-dependent adhesion molecules. They are critical for
establishing
and maintaining intercellular connections, and they appear to be crucial to the spatial
segregation of cell types and to the organization of animal form.
b) The cadherins are anchored inside the cell by a complex of proteins called catenins and the
cadherin-catenin complex forms the classic adherens junctions that help hold epithelial cells
together.
Cell Migration: a) migration involves the adhesion of the cell to its extracellular substrate. The
moving cell needs
something to push on, and attaches to the surrounding matrix.
b) Integrins span the cell membrane, connecting the extracellular matrix outside the cell to the

2. actin cytoskeleton on the inside of the cell. These connections of actin to integrin form focal
adhesions on the cell membrane where the membrane contacts the extracellular matrix.
c) Myosin and its regulators provide the motive force along these actin microfilaments.they are
linked with the lamellipodial actin at the sites of adhesion.
d) Release of adhesions in the rear, allowing the cell to migrate in the forward direction. It is
probable that stretch-sensitive calcium channels are opened and that the released calcium ions
activate proteases that destroy the focal adhesion sites.