MOLECULAR BIOLOGY OF THE CELL, SIXTH EDITION
CHAPTER 21: DEVELOPMENT OF MULTICELLULAR
ORGANISMS
1. Plants and animals use different developmental strategies and have very different ways of
life. In which of the following fundamental cellular processes during development are plants
most different to animals?
A. Cell proliferation
B. Cell–cell interactions
C. Cell specialization
D. Cell movement
2. The simplified drawing below depicts early stages of animal development. Indicate which
letter (A to E) in the drawing corresponds to each of the following terms. Your answer would be
a five-letter string composed of letters A to E only, e.g. ECDBA.
D
E
C
A B
( ) Blastula
( ) Ectoderm
( ) Endoderm
( ) Mesoderm
( ) Gastrula
3. Indicate whether each of the following organs or tissues arises from ectoderm (C),
mesoderm (M), or endoderm (N). Your answer would be a four-letter string composed of letters
C, M, and N only, e.g. MMCC.
, ( ) Blood
( ) Liver and pancreas
( ) Brain
( ) Bone and cartilage
4. Indicate true (T) and false (F) statements below regarding animal development. Your
answer would be a four-letter string composed of letters T and F only, e.g. FFFF.
( ) A fertilized egg is totipotent.
( ) Differences in their regulatory DNA can largely explain the differences between
animal species.
( ) Inductive signaling is mostly mediated through G-protein-coupled receptors.
( ) A cell’s response to a signal depends on its exposure to other signals at that present
time as well as in the past.
5. Imagine a morphogen gradient established from left to right in a field of cells in a
developing tissue, as shown in the following schematic diagram. Below a first threshold of
morphogen concentration, cells do not respond to the morphogen and express gene “red” by
default. Cells exposed to morphogen concentrations above this threshold respond by expressing
gene “white” instead, while those exposed to even higher concentrations, above a second
threshold, express gene “blue.” As shown, the initial pattern resembles a French flag with
equally wide blue, white, and red expression domains. With no other change, if the diffusion rate
of the morphogen is increased (by a modification that decreases its affinity for heparan sulfate
proteoglycans, for example), the gradient profile changes from the gray curve to the black curve,
as indicated. Under this new condition, indicate whether each of the following would be
expected to increase (I), decrease (D), or remain unchanged (U) in its range. Your answer would
be a three-letter string composed of letters I, D, and U only, e.g. UUI.
Position
concentration
Morphogen
Initial pattern
, ( ) Blue expression domain
( ) White expression domain
( ) Red expression domain
6. Indicate whether each of the following descriptions better applies to patterning by lateral
inhibition (L), reaction-diffusion systems (R), or sequential induction (S). Your answer would be
a four-letter string composed of letters L, R, and S only, e.g. SSRR.
( ) It does NOT generate asymmetrical patterns from an initial noisy field.
( ) It is based on short-range activation and long-range inhibition.
( ) It can readily generate complex patterns resembling the spots of a leopard or stripes
of a zebra.
( ) It is commonly mediated by Notch signaling.
7. Indicate whether each of the following descriptions better applies to these poles
established in an early embryo: anterior (A), posterior (P), dorsal (D), ventral (V), animal (N), or
vegetal (G). Your answer would be a six-letter string composed of letters A, D, G, N, P, and V
only, e.g. ADGPVN.
( ) It defines the part to become internalized in gastrulation.
( ) It defines the parts to remain external.
( ) It defines the location of the future head.
( ) It defines the location of the future tail.
( ) It defines the location of the future belly.
( ) It defines the location of the future back.
8. Sort the following organisms from the least to the most degree of asymmetry in the
unfertilized egg (i.e. pre-defined axes of polarization). Your answer would be a three-letter string
composed of letters A to C only, e.g. BCA.
(A) M. musculus
(B) D. melanogaster
(C) X. laevis
9. Sort the following primary axes in the order that they are established during the
development of Xenopus laevis. Your answer would be a three-letter string composed of letters
A to C only, e.g. ACB.
(A) A-P
, (B) D-V
(C) A-V
10. Cortical rotation following fertilization in X. laevis places the …(1) pole at the point of
sperm entry, while Wnt11 mRNA is transported to the …(2) pole.
A. 1: anterior; 2: posterior
B. 1: posterior; 2: anterior
C. 1: animal; 2: vegetal
D. 1: dorsal; 2: ventral
E. 1: ventral; 2: dorsal
11. Which of the following is true regarding maternal-effect genes?
A. Bicoid and Nanos are maternal-effect genes.
B. A female homozygous for a loss-of-function maternal-effect gene mutation can be
fully normal, but her offspring will show the phenotype.
C. The offspring of a female homozygous for a loss-of-function maternal-effect gene
mutation will show the phenotype regardless of the paternal genotype.
D. The second-generation offspring of a male homozygous for a loss-of-function
maternal-effect gene mutation can show the phenotype.
E. All of the above.
12. Indicate whether each of the following descriptions better applies to egg-polarity genes
(E), gap genes (G), pair-rule genes (P), or segment-polarity genes (S). Your answer would be a
four-letter string composed of letters E, G, P, and S only, e.g. SSGG.
( ) Mutations in these genes show a maternal effect.
( ) Mutations in these genes leave the embryo with only half the number of normal
segments.
( ) Mutations in these genes produce a normal number of segments but with part of each
segment replaced by a mirror-image duplicate of other parts of the segment.
( ) Mutations in these genes can eliminate one or two groups of adjacent segments
altogether.
13. In a developing Drosophila melanogaster embryo, a hierarchy of gene regulatory
interactions subdivides the embryo to regulate progressively finer details of patterning. For each
of the following proteins, indicate which expression pattern (1 to 4) in the schematic drawing
CHAPTER 21: DEVELOPMENT OF MULTICELLULAR
ORGANISMS
1. Plants and animals use different developmental strategies and have very different ways of
life. In which of the following fundamental cellular processes during development are plants
most different to animals?
A. Cell proliferation
B. Cell–cell interactions
C. Cell specialization
D. Cell movement
2. The simplified drawing below depicts early stages of animal development. Indicate which
letter (A to E) in the drawing corresponds to each of the following terms. Your answer would be
a five-letter string composed of letters A to E only, e.g. ECDBA.
D
E
C
A B
( ) Blastula
( ) Ectoderm
( ) Endoderm
( ) Mesoderm
( ) Gastrula
3. Indicate whether each of the following organs or tissues arises from ectoderm (C),
mesoderm (M), or endoderm (N). Your answer would be a four-letter string composed of letters
C, M, and N only, e.g. MMCC.
, ( ) Blood
( ) Liver and pancreas
( ) Brain
( ) Bone and cartilage
4. Indicate true (T) and false (F) statements below regarding animal development. Your
answer would be a four-letter string composed of letters T and F only, e.g. FFFF.
( ) A fertilized egg is totipotent.
( ) Differences in their regulatory DNA can largely explain the differences between
animal species.
( ) Inductive signaling is mostly mediated through G-protein-coupled receptors.
( ) A cell’s response to a signal depends on its exposure to other signals at that present
time as well as in the past.
5. Imagine a morphogen gradient established from left to right in a field of cells in a
developing tissue, as shown in the following schematic diagram. Below a first threshold of
morphogen concentration, cells do not respond to the morphogen and express gene “red” by
default. Cells exposed to morphogen concentrations above this threshold respond by expressing
gene “white” instead, while those exposed to even higher concentrations, above a second
threshold, express gene “blue.” As shown, the initial pattern resembles a French flag with
equally wide blue, white, and red expression domains. With no other change, if the diffusion rate
of the morphogen is increased (by a modification that decreases its affinity for heparan sulfate
proteoglycans, for example), the gradient profile changes from the gray curve to the black curve,
as indicated. Under this new condition, indicate whether each of the following would be
expected to increase (I), decrease (D), or remain unchanged (U) in its range. Your answer would
be a three-letter string composed of letters I, D, and U only, e.g. UUI.
Position
concentration
Morphogen
Initial pattern
, ( ) Blue expression domain
( ) White expression domain
( ) Red expression domain
6. Indicate whether each of the following descriptions better applies to patterning by lateral
inhibition (L), reaction-diffusion systems (R), or sequential induction (S). Your answer would be
a four-letter string composed of letters L, R, and S only, e.g. SSRR.
( ) It does NOT generate asymmetrical patterns from an initial noisy field.
( ) It is based on short-range activation and long-range inhibition.
( ) It can readily generate complex patterns resembling the spots of a leopard or stripes
of a zebra.
( ) It is commonly mediated by Notch signaling.
7. Indicate whether each of the following descriptions better applies to these poles
established in an early embryo: anterior (A), posterior (P), dorsal (D), ventral (V), animal (N), or
vegetal (G). Your answer would be a six-letter string composed of letters A, D, G, N, P, and V
only, e.g. ADGPVN.
( ) It defines the part to become internalized in gastrulation.
( ) It defines the parts to remain external.
( ) It defines the location of the future head.
( ) It defines the location of the future tail.
( ) It defines the location of the future belly.
( ) It defines the location of the future back.
8. Sort the following organisms from the least to the most degree of asymmetry in the
unfertilized egg (i.e. pre-defined axes of polarization). Your answer would be a three-letter string
composed of letters A to C only, e.g. BCA.
(A) M. musculus
(B) D. melanogaster
(C) X. laevis
9. Sort the following primary axes in the order that they are established during the
development of Xenopus laevis. Your answer would be a three-letter string composed of letters
A to C only, e.g. ACB.
(A) A-P
, (B) D-V
(C) A-V
10. Cortical rotation following fertilization in X. laevis places the …(1) pole at the point of
sperm entry, while Wnt11 mRNA is transported to the …(2) pole.
A. 1: anterior; 2: posterior
B. 1: posterior; 2: anterior
C. 1: animal; 2: vegetal
D. 1: dorsal; 2: ventral
E. 1: ventral; 2: dorsal
11. Which of the following is true regarding maternal-effect genes?
A. Bicoid and Nanos are maternal-effect genes.
B. A female homozygous for a loss-of-function maternal-effect gene mutation can be
fully normal, but her offspring will show the phenotype.
C. The offspring of a female homozygous for a loss-of-function maternal-effect gene
mutation will show the phenotype regardless of the paternal genotype.
D. The second-generation offspring of a male homozygous for a loss-of-function
maternal-effect gene mutation can show the phenotype.
E. All of the above.
12. Indicate whether each of the following descriptions better applies to egg-polarity genes
(E), gap genes (G), pair-rule genes (P), or segment-polarity genes (S). Your answer would be a
four-letter string composed of letters E, G, P, and S only, e.g. SSGG.
( ) Mutations in these genes show a maternal effect.
( ) Mutations in these genes leave the embryo with only half the number of normal
segments.
( ) Mutations in these genes produce a normal number of segments but with part of each
segment replaced by a mirror-image duplicate of other parts of the segment.
( ) Mutations in these genes can eliminate one or two groups of adjacent segments
altogether.
13. In a developing Drosophila melanogaster embryo, a hierarchy of gene regulatory
interactions subdivides the embryo to regulate progressively finer details of patterning. For each
of the following proteins, indicate which expression pattern (1 to 4) in the schematic drawing
