BIO 529 S05
Exam I
Name______________________
ID #_______________________
1. Fill in the blanks with the best answer from the list provided. Terms may be used more than
once. (1 pt each)
epigenesis
fate map
induction
soma
determination
gastrulation
morphogen
autonomous
cloning
RNAi
specification
juxtacrine
pluripotence
commitment
nematode
enhancer
Pax6
vertebrate
Morphogen
Microarray
Syncytium
Regulative
Pluripotence
Wnt
Metazoan
Juxtacrine
Methylation
Pax6
Gastrulation
Determination
Deuterostome
Paracrine
RNAi
Cleavage
Vertebrate
Metazoan
Deuterostome
Chordate
embryo
notochord
preformation
metazoan
conditional
microarray
morphogenesis
blastula
totipotence
mitosis
Wnt
deuterostome
TGF-
epithelium
PCR
competence
amphibian
FGF
epiboly
diploblast
zygote
cleavage
stem cell
morpholino
germ line
imprinting
instructive
meiosis
chordate
permissive
arthropod
BMP4
endocrine
Hedgehog
differentiation
Smad
chimera
triploblast
organogenesis
larva
protostome
regulative
in situ hybridization
mosaic
JAK-STAT
syncytium
reverse transcription
mesenchyme
receptor tyrosine kinase
Northern blotting
paracrine
urochordate
targeted knock-out
methylation
A molecule that induces different fates, depending on concentration
Technique that compares levels of mRNAs of many genes at once
A large number of nuclei that share a common cytoplasm
Developmental mode in which the organism can compensate for loss
of the precursors for a particular tissue
Ability of a cell to adopt many alternative fates
Signaling pathway that includes APC and -catenin
An animal that undergoes a true embryonic stage
Signaling mechanism that requires direct cell contact
DNA modification often associated with transcriptional silencing
A protein required for competence in lens development in mice
Embryonic stage during which cell movements begin
Irreversible commitment to a cell fate
Animal that develops “anus-first” (blastopore forms anus)
Short range signaling mechanism that does not require cell contact
Technique that uses a small segment of double stranded nucleic acid
to inhibit the function of a specific gene
Early embryonic stage marked by rapid cell divisions
Terms from the above list that describe all mammals
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BIO 529 S05
Exam I
Name______________________
ID #_______________________
For all remaining questions, you must show your work or explain your reasoning to receive
any partial credit.
2. Most eukaryotic embryos are comprised of three primary germ layers.
a. Name the three germ layers and provide two examples of adult tissues derived from each.
(6 pts)
Ectoderm: epidermis, nervous system, neural crest
Mesoderm: notochord, bone, muscle, kidney, blood cells
Endoderm: respiratory & digestive tracts, thyroid, pancreas
b. What is the additional lineage (other than the three primary germ layers) found in
metazoans? To what cell type(s) does it give rise. (4 pts)
Germline: gametes (egg or sperm)
3. A number of model organisms for developmental biology were described early in the course.
Each organism has its own strengths and weaknesses for such studies.
a. Describe 3 characteristics that make the nematode, C. elegans, attractive for the study of
development. (3 pts)
 Short life cycle and embryogenesis
 Transparent at all stages
 Few total cells, but complete array of types
 Fate mapped
 Genome sequence completed
 Small size, easy & cheap to propagate
 Excellent genetics
 Easy to make transgenics
b. Describe 3 characteristics that make the frog, Xenopus laevis, attractive for the study of
development. (3 pts)
 Rapid embryogenesis
 Very large egg
 Surgically manipulable
 Easy to regulate fertilization
 Resistant to infection
 Regions are differentially pigmented
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BIO 529 S05
Exam I
Name______________________
ID #_______________________
4. Name the 3 steps of differentiation and indicate what properties distinguish them. (9 pts)
Specification- reversible commitment to fate- Cell in a neutral environment will continue
on to adopt the specified fate.
Determination- irreversible commitment to fate- Cell in a new (non-neutral) environment
will continue to adopt the originally determined fate.
Differentiation- adoption of fate- Cell takes on molecular, morphological, and functional
characteristics of fate.
5. It has been said that differential gene activity is the key to development of distinct tissues.
What does this mean? (8 pts)
Essentially all cells of the organism carry a complete genome, thus have the potential to form
any possible cell fate. However, each type of cell expresses a unique set of gene products. It
is this unique set of different gene activities that distinguish one cell type from another.
6. Gene activity can be regulated at many different stages. Name three levels at which gene
activity can be regulated. Which level is most common? (8 pts)




Transcriptional regulation (most common)
Post-transcriptional (eg. RNA splicing, polyadenylation, export, stability)
Translational
Post-translational (eg. Protein modification, subcellular localization, stability)
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BIO 529 S05
Exam I
Name______________________
ID #_______________________
5. In the late 19th century, August Weismann proposed his theory of inheritance that was based
on the idea of “nuclear determinants”.
a. Briefly explain Weismann’s theory of inheritance. (6 pts)
Weismann believed that the zygote contains nuclear determinants that direct the function
of each cell type. During division and development, the determinants are partitioned
unequally to the cells that will utilize those determinants for their final function. Only the
germ cells would retain all determinants for the organism.
b. What predictions does Weismann’s theory make regarding mosaic vs. regulative
development? (6 pts)
This model mandates mosaic development and predicts that regulative development
would not be possible.
c. Briefly describe an experiment that proves Weismann’s theory to be in error. Be sure to
indicate how the results of the experiment contradict Weismann. (6 pts)
Several experiments disprove Weismann’s theory because they illustrate that cells retain
the necessary information to make all cell types. Driesch was the first to contradict
Weismann by isolating the 4 cells of a sea urchin embryo. Each developed into an
essentially complete larva, thus showing that each cell of the 4-celled sea urchin embryo has
the capacity to build a whole organism. More recent experiments, including organismal
clonal, have further contradicted the partitioning of determinants during development.
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BIO 529 S05
Exam I
Name______________________
ID #_______________________
8. Furuta and Hogan reported that BMP4 is an important molecule in the production of lens in
mice. They reached this conclusion because they examined the developing eyes of mice
mutant for BMP4 and found that the lens never forms.
a. To what molecular family does BMP4 belong? (3 pts)
TGF-
b. Upon BMP4 signaling, what transcription factor family would you expect to be activated
in the responding cell? (2 pts)
Smad
c. After learning that lens does not develop in BMP4 mutant mice, Furuta and Hogan wanted
to know whether BMP4 is an inducer that is provided specifically by the optic vesicle.
Describe the experiment they performed to address this question and their conclusion. (8 pts)
The experiment performed to most directly address this question was the recombination
experiment mixing BMP4 mutant optic vesicle with wild-type head ectoderm. They
expected that if BMP4 from the optic vesicle must induce lens, that this combination of tissue
would fail to make lens. However, their results were ambiguous: about a quarter of the
explants formed some lens, as opposed to more than 60% producing lens in the reciprocal
transplant. The authors suggest that BMP4 from the optic vesicle probably is necessary, but
that the wild-type ectoderm may have already been exposed to sufficient BMP4 prior to the
recombination.
9. At the mid-gastrula stage of a Xenopus embryo, the presumptive eye tissue is transplanted
into a new embryo in the region that gives rise to the somitic mesoderm. The resulting
transplanted tissue becomes eye tissue. What does that tell you about the presumptive eye
tissue of Xenopus at the mid-gastrula stage? (8 pts)
The presumptive eye tissue must already be determined to become eye by the midgastrula stage.
BONUS: Name two members of the vertebrate hedgehog family of ligands. (4 pts, all or none)
Indian hedgehog, desert hedgehog, and sonic hedgehog
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