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Question 1

This chapter discusses the embryonic development of Drosophila melanogaster. How long does embryonic development take in this organism?

a) One hour.

b) Three hours.

c) One day.

d) Ten days.

e) Nine months.

Question 2

The portion of the blastoderm-stage embryo which will give rise to most ectodermal, mesodermal, and endodermal tissues is called the:

a) ventral.

b) germ band.

c) imaginal discs.

d) amnioserosa.

e) germ line.

Question 3

The development of the antero-posterior axis of Drosophila is initiated when:

a) the mother packages bicoid and nanos mRNA into the developing oocyte.

b) the Toll receptor is activated after fertilization, leading to nuclear localization of Dorsal protein.

c) the terminal group protein Torso sets up the anterior and posterior poles of the embryo.

d) the homeotic genes specify the fate of individual segments.

e) the sperm enters the micropile at the anterior end, thus specifying the antero-posterior axis.

Question 4

Which would lead to a dorsalized embryo? (Recall that genes in Drosophila are named for their mutant phenotype.)

a) Dorsal mutant.

b) Cactus mutant.

c) Toll mutant.

d) Spätzle mutant.

e) Bicoid mutant.

Question 5

A gap gene mutation might cause which of the following defects in the embryonic body plan?

a) Every other segment would be missing, resulting in T1, T3, A2, A4, etc. but no T2, A1, A3, and so on.

b) Segments A2 through A6 would be missing, but the rest of the pattern is essentially normal.

c) No segmentation would be evident.

d) Patterning within each segment would be abnormal, causing for example denticle belts to form across the entire segment.

e) The identity of one or more segments would be transformed to that of a different segment, such that the T3 leg would transformed to a T2 leg.

Question 6

The activation of zygotic hunchback expression by Bicoid protein illustrates what principle in the establishment of positional information in embryos?

a) The mother can influence development through the packaging of materials into the egg.

b) A gradient of a protein can activate a gene in a discrete region of an embryo through a threshold effect.

c) The identity of segments in the embryo is a reflection of their position in the embryo.

d) A cascade of gene activations occurs in the syncitial blastoderm.

e) Genes are activated or repressed by the binding of transcription factors to their regulatory regions.

Question 7

The portion of the Drosophila body plan which will produce the wing is called:

a) telson.

b) dorsal.

c) abdomen.

d) thorax.

e) neurectoderm.

Question 8

The adult body plan of the fly is based on reiterating structures called segments; segment precursors (parasegments) are first positioned at the cell-by-cell level by which group of genes?

a) Maternal genes such as bicoid.

b) Gap genes such as Kruppel.

c) Pair-rule genes such as even-skipped.

d) Segmentation genes such as engrailed.

e) Homeotic genes such as antennapedi.

Question 9

Mutations in homeotic genes can lead to what type of developmental defect?

a) The anterior portion of the embryo does not develop.

b) Several adjacent segments will be missing from an otherwise intact embryo.

c) The embryo will develop with every other segment failing to form.

d) Segment and compartment boundaries will fail to form.

e) The development of segments will be changed wholesale from their normal identity to that of a different segment.

Question 10

Which of the following, first discovered through mutagenesis studies in Drosophila, also function in the development of mammals like ourselves?

a) Hedgehog.

b) Homeobox genes.

c) The Wnt family.

d) The Toll signalling pathway.

e) All of the above.

Oxford University Press, Online Resource Centre, Chapter 02.

Chapter 02

Instructions