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Return to Principles of Development 6e Student Resources
Chapter 6 Self-test questions
Development of nematodes and sea urchins
What is the difference between apoptosis and necrosis?
Apoptosis is a controlled program of cellular destruction; necrosis is cell death due to damage.
Apoptosis is a property of all differentiated cells; necrosis only occurs to undifferentiated cells.
Apoptosis is cell death due to damage that occurs during embryogenesis; necrosis is cell death due to damage that occurs during adulthood.
Apoptosis is a term used to refer to necrosis that happens during development.
What is the role of caspases in apoptosis?
Caspases are enzymes that are inactivated during apoptosis, and in their absence the cell dies.
Caspases are inhibitors of apoptosis; the destruction of the caspases causes apoptosis to begin.
Caspases are mitochondrial enzymes that are released when apoptosis is triggered.
Caspases are proteases that carry out the controlled destruction of the cell's components during apoptosis.
is best known for
its formation of an inductive signaling center analogous to the organizer of
its fully defined cell lineage during development
the large size and easy manipulation of its blastomeres
its mechanisms of metamorphosis
P granules of nematodes are
determinants of the antero-posterior axis
determinants of the germ line
precursors of TGF-â family signaling proteins
remnants of the sperm pronucleus
In flies, frogs, and chicks, gradients of morphogens determine the future antero-posterior and dorso-ventral axes of the developing embryo. How is the antero-posterior axis determined in
Bicoid protein is translated in the anterior of the fertilized egg, leading to a gradient that determines the antero-posterior axis.
Opposing gradients of chordin and BMP-4 establish the antero-posterior axis.
Sperm entry leads to a reorganization of the cytoskeleton and redistribution of maternally packaged PAR proteins, which in turn determine the antero-posterior axis.
â-catenin becomes localized to the nucleus in the future anterior cells after fertilization.
Do Hox genes have a role in the development of
has Hox genes but none of them are used during development
has 4 clusters of Hox genes, just like mammals, that are required for specification of the identity of structures during embryogenesis
Yes, but only one Hox gene is required in the embryo; the others provide positional identity in the larva
Yes, and their genetic organization and role in development is nearly identical to that in
What are the
versions of the Hox genes.
are genes that are named for their control of the first division, and hence the lineage of the AB and P1 cells.
controls the timing of transcription of
, and so is referred to a 'heterochronic' gene.
encodes a miRNA that represses
translation, which in turn regulates timing during larval development.
Which of these model organisms is closest evolutionarily to humans?
Fruit flies, because of their sophisticated nervous system and the presence of legs.
Plants, because their early divergence from animal lineages means they are closely related to animals, especially humans.
Sea urchins, despite their radial symmetry and lack of limbs.
Worms, despite their few cells, small genomes, and abbreviated complement of Hox genes.
statement best describes gastrulation in sea urchins?
Gastrulation is initiated by invagination of the micromeres at the vegetal pole.
The mouth of the pluteus larva will form from mesomeres on the oral side of the 60-cell embryo.
The gut will form from the macromeres at the 16-cell stage.
All of the options given are true.
During early sea urchin development, which embryonic cells have similar organizer activity to that of the amphibian Spemann organizer?
cells of Veg1 tier
A classical view of development sees embryos as either 'mosaic' or 'regulative'. Which of the following statements is true?
is a mosaic embryo with cell-cell interactions whereas sea urchin embryos are regulative
and sea urchin embryos are regulative
is a regulative embryo whereas sea urchin is mosaic
is a strictly mosaic embryo whereas sea urchin is regulative
In which way is the organizer region in the sea urchin similar to that of frogs?
It accumulates â-catenin, which in turn activates the expression of cell-cell signaling molecules.
It forms near the dorsal lip of the blastopore.
It induces the dorso-ventral axis.
It will express high levels of Nodal.
In the sea urchin embryo, the function of BMP and Nodal is
to establish the animal-vegetal axis
to specify mesoderm
to control the early patterns of cell division
to organize the oral-aboral axis
Which of the following statements explains why gain-of-function mutation of Pmar1 results in a vegetalized embryo:
Beta-catenin is at highest concentration in the micromeres
Pmar1 is activated by maternal beta-catenin and Otx
HesC transcription is repressed; skeletogenic genes are activated in all cells
HesC is activated; Delta protein induces mesodermal specification
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