In Drosophila after ~100 minutes postfertilization, the embryo looks like the following diagram, with all nuclei having moved to the periphery and, subsequently, four of the nuclei being sequestered at the posterior end.
Drosophila embryo after about 2 hours.
B) nuclei in the cortex that has not undergone cytokinesis.
C) nuclei in the cortex forming a single-cell layer over the surface.
D) an embryo with segmentation beginning to be apparent.
Answer: B
B) the germ cells of the adult.
C) mouthparts.
D) antennae.
E) wing primordial.
Answer: B
B) homeotic genes.
C) maternal effect genes.
D) zygotic genes.
E) all of the above.
Answer: C
B) use of pair-rule genes to divide the embryo into stripes, each of which will become two segments.
C) use of zygotic segment polarity genes to divide each segment into anterior and posterior halves.
D) enclosure of the nuclei in membranes, forming a single layer over the surface.
E) separation of head, thoracic, and abdominal segments of the embryo.
Answer: D
B) homeotic developmental control.
C) the blockage of cell-to-cell communication.
D) homeotic developmental control and the blockage of cell-to-cell communication.
E) a hierarchy of gene expression and the blockage of cell-to-cell communication.
Answer: A
Drosophila embryo after about 2 hours.
1) At this point, the embryo is characterized as
A) a first-stage larva.B) nuclei in the cortex that has not undergone cytokinesis.
C) nuclei in the cortex forming a single-cell layer over the surface.
D) an embryo with segmentation beginning to be apparent.
Answer: B
2) The four sequestered cells at one end are most probably destined to become
A) the legs of the adult fly.B) the germ cells of the adult.
C) mouthparts.
D) antennae.
E) wing primordial.
Answer: B
3) Formation of the pole cells (the four sequestered cells) demonstrates the role of
A) segmentation genes.B) homeotic genes.
C) maternal effect genes.
D) zygotic genes.
E) all of the above.
Answer: C
4) The next step after the embryo is formed would be
A) division of the embryo into five broad regions.B) use of pair-rule genes to divide the embryo into stripes, each of which will become two segments.
C) use of zygotic segment polarity genes to divide each segment into anterior and posterior halves.
D) enclosure of the nuclei in membranes, forming a single layer over the surface.
E) separation of head, thoracic, and abdominal segments of the embryo.
Answer: D
5) The developmental stages described for Drosophila illustrate
A) a hierarchy of gene expression.B) homeotic developmental control.
C) the blockage of cell-to-cell communication.
D) homeotic developmental control and the blockage of cell-to-cell communication.
E) a hierarchy of gene expression and the blockage of cell-to-cell communication.
Answer: A