BIO 349 Developmental Biology (K. Kalthoff)

Exams Fall 1994

First Midterm Exam (11 October 1994)

EXCHANGE WORDS (2 points per pair)

The following statements are erroneous. However, each one can be corrected by exchanging two single words. Circle these two words within each statement.

1/2. The animal pronucleus of an egg is defined by the excentric [off-center] position of the female pole and the polar bodies.

3/4. In the egg chambers of meroistic insects, the follicle cells synthesize RNA for the oocyte while the nurse cells contribute to vitellogenesis.

5/6. The fast block to polyspermy works by a change in cortical membrane potential while the slow block is part of the plasma reaction.

7/8. According to the principle of biological mechanisms, a given synergistic function is often supported by several independent mechanisms.

MULTIPLE CHOICE (1 point each)

In the following questions or statements, circle the letter associated with the one answer or version of the statement that you consider to be the most adequate.

9. Sertoli cells are found
a. in insect ovaries
b. interspersed between seminiferous tubules in vertebrate testis
c. within the seminiferous tubules in vertebrate testis
d. none of the above is correct

10. Which two membranes fuse during the acrosomal reaction?
a. acrosomal membrane with egg plasma membrane
b. sperm plasma membrane with egg plasma membrane
c. both of the above are correct
d. none of the above is correct

11. Superficial cleavage is characteristic of
a. amphibians
b. birds
c. insects
d. mammals

12. Localization of cytoplasmic determinants may occur
a. during oogenesis
b. upon fertilization
c. during cleavage
d. all of the above

13. The gray crescent in amphibian eggs
a. is formed near the equator on the future dorsal side
b. contains cytoplasmic determinants for the blastopore
c. both of the above are correct
d. none of the above is correct

14. Localized cytoplasmic determinants are demonstrated by
a. autoradiography
b. immunostaining
c. both of the above are correct
d. none of the above is correct

15. Embryonic cells are determined by
a. localized cytoplasmic components
b. induction
c. both of the above are correct
d. none of the above is correct

16. Imaginal discs are found in
a. adult insects
b. insect larvae
c. mammalian embryos
d. salamander lenses

PICK THE ODD STATEMENT (1 point each)

For the following questions, either three of the statements are correct and one is false, or three are false and one is correct. Pick the one odd statement, be it correct or false, and circle the respective letter.

17. Polyspermy
a. Polyspermy means a male produces more sperm than eggs are produced by a female of the same species.
b. Polyspermy is avoided in most animals because it leads to abnormal chromosome numbers.
c. A change in the electric potential across the egg membrane may serve as a fast block to polyspermy.
d. The cortical granule reaction serves as a slow block to polyspermy.

18. Determined State of Amphibian Cells
a. Pregastrula dorsal animal cells are determined to form neural plate.
b. Postgastrula dorsal animal cells are determined to form neural plate.
c. Early dorsal blastopore lip is determined to form posterior chordamesoderm.
d. Late dorsal blastopore lip is determined to form anterior chordamesoderm.

19. Regulatory and Mosaic Eggs
a. In mosaic eggs the potency of most blastomeres is quickly limited to its fate.
b. Mosaic eggs are characterized by twinning after blastomere separation.
c. In regulatory eggs the potency of blastomeres is greater than their fate.
d. Regulatory eggs rely more on induction than mosaic eggs.

20. Induction
a. Induction is an interaction between cells or tissues that changes the determined state of at least one partner.
b. The cell (tissue) that changes its state of determination is always the inducing tissue.
c. Most inductive interactions occur during oogenesis.
d. In the frog blastula, animal cells induce their vegetal neighbors to form mesoderm.

21-30. SHORT ESSAY (max. 10 points) Spiral Cleavage/Maternal Effect

A. Describe the first three divisions of an embryo with spiral cleavage. Add small drawings to show the orientation of the cleavage planes relative to the animal-vegetal axis, the relative sizes of the blastomeres, and their configuration relative to each other.
B. Certain snail mutants show abnormally oriented cleavage planes. Is cleavage plane orientation determined by the genotype of the maternal organism, the paternal organism, or the embryo? Support your answer with results of genetic crossing experiments.
C. Which conclusions can be drawn from the results with regard to the factors that orient cleavage planes?

31-40. SHORT ESSAY (max. 10 points) Gene Control by Cytoplasmic Environment

To analyze the effect of the cytoplasmic environment on gene expression, nuclei were transplanted from frog kidney cells to newt oocytes.

A. How did the investigators identify individual gene products?
B. Which groups of gene products did the investigators distinguish?
C. What groups of gene products encoded by frog nuclei were synthesizedčor not synthesizedč in the host oocytes?
D. What conclusions can be drawn from the results?M
E. Offer an explanation why some but not all appropriate donor genes were affected by the host cytoplasm.

41-50. SHORT ESSAY (max. 10 points) Convergent Extension

A. Describe what happens to the shape of an epithelium that undergoes convergent extension.
B. Describe two activities of individual cells that can bring about convergent extension of an epithelium.
C,D. Outline two experiments that demonstrate the occurrence of convergent extension in the dorsal involuting marginal zone of frog embryos and in the elongating archenteron of sea urchin embryos.

Second Midterm Exam (8 November 1994)

MATCH UP (max. 10 points)

The following is a list of adult structures (1-10) and their embryonic precursors (a-j). Match up by entering one appropriate letter in each of the spaces behind the numbers. Note that some precursors may be 'used' several times and others not at all.

1. _____ adrenal medulla

2. _____ blood vessels

3. _____ dorsal root ganglia

4. _____ hypodermis

5. _____ lens

6. _____ lung (inner epithelium)

7. _____ melanocytes

8. _____ skeletal muscles of

9. _____ smooth muscle of intestine

10. _____ vertebra

a. dermatome

b. endoderm

c. epidermal ectoderm

d. myotome

e. nephrotome

f. neural crest cells

g. epidermal placode (pigment cells)

h. sklerotome the trunk

i. somatic lateral mesoderm

j. visceral lateral mesoderm

MULTIPLE CHOICE (1 point each) In the following questions or statements, circle the letter associated with the one answer or version of the statement that you consider to be the most adequate.

11. The surge in protein synthesis after fertilization of sea urchin eggs is mediated by
a. a shift of mRNAs from sub-ribosomal RNP particles into the polysomes
b. a rise in cellular pH
c. both of the above are correct
d. none of the above is correct

12. The cortical units of Paramecium normally multiply by
a. cortical picking
b. directed assembly
c. self-assembly
d. none of the above

13. Transgenic mice can be generated
a. from transformed embryonic stem cells
b. by injecting cloned DNA into an egg pronucleus
c. both of the above are correct
d. none of the above is correct

14. Which of the following processes is regulated by RNA-binding proteins?
a. splicing of pre-mRNA
b. RNA translation
c. RNA degradation
d. all of the above

15. The formation of the floor plate in the spinal cord is induced by the
a. archenteron
b. marginal layer
c. neural crest
d. none of the above

PICK THE ODD STATEMENT (1 point each)

The following are groups of statements. In each group, one statement is correct and three are false, OR three are correct and one is false. Find out the one odd statement, be it false of correct, and circle the respective letter.

16. Self-Assembly
a. Self-assembly is defined as an assembly in which molecules snap together spontaneously.
b. Microtubules self-assemble from tubulin dimers.
c. Ribosomes self-assemble from their RNA and protein components.
d. Bacteria self-assemble from DNA and proteins.

17. Eukaryotic Gene Structure
a. The transcribed region of most eukaryotic genes contains introns and exons.
b. The TATA box is an enhancer sequence.
c. The introns are spliced out of the genomic DNA before transcription.
d. Each gene has only one promoter.

18. RNA and Protein Synthesis in Early Embryos
a. The utilization of maternal mRNA in early embryos is indicated by the existence of maternal effect mutants.
b. Enucleated egg fragments are capable of protein synthesis.
c. Many animal embryos synthesize RNA actively while protein synthesis is immeasurable.
d. The rate of protein synthesis increases after fertilization.

19. Sex Determination in Drosophila
a. The sex of fruit flies is determined by the presence versus absence of the Y chromosome.
b. The Sex-lethal gene maintains the splicing pattern of its pre-mRNA by its own protein.
c. The transcript of the double sex (dsx) gene is processed into either a male specific or a female-specific mRNA.
d. The splicing of the dsx mRNA is regulated by transformer (tra) protein.

20. The ductus arteriosus
a. is a shunt between the left pulmonary artery and the aorta.
b. becomes the ligamentum arteriosum after birth.
c. is embryonically derived from the sixth aortic arch.
d. pumps blood into the lungs.

21-30. SHORT ESSAY (max. 10 points) Neural Induction

A. Outline the organizer experiment of Spemann and Mangold (1924).
B. How did the investigators distinguish which structures were formed by transplant versus host tissue?
C. Describe the results obtained and the conclusions drawn.
D. Describe the two pathways (planar vs. perpendicular), along which the inducing signals may travel.

31-40. SHORT ESSAY (max. 10 points) Patterning Genes in Drosophila

In Drosophila eggs, maternally encoded bicoid (bcd) protein acts as a transcription factor enhancing the expression of the embryonic hunchback (hb) gene.
A. Briefly characterize the functional relationship between bicoid protein and the hunchback+ gene in the Drosophila embryo.
B. What was learned about this relationship using genetic analysis and an antibody against hunchback protein?

41-50. SHORT ESSAY (max. 10 points) Translational Control of Protamine Synthesis

Describe the experiments that demonstrated longevity and delayed translation of protamine mRNA during mouse spermatogenesis. In particular, which experimental strategy was used to identify the location of the RNA sequence that confers these properties to protamine mRNA?

Final Exam (14 December 1994)

MULTIPLE CHOICE (1 point each)

In the following questions or statements, circle the letter associated with the one answer or version of the statement that you consider to be the most adequate.

1. Mechanisms of translational control include
a. change of intracellular pH
b. conserving or inactivating inactivation eukaryotic initiation factors
c. sequestration of mRNA
d. all of the above

2. Which of the following organelles are capable of self-assembly?
a. microtubules
b. ribosomes
c. chromatin
d. all of the above

3. Products of oncogenes were found to be
a. growth factors
b. growth factor receptors
c. signal proteins
d. all of the above are correct

4. The Barr body (sex chromatin)
a. determines the formation of pole cells in insect embryos
b. is an inactivated X-chromosome
c. marks the animal pole
d. none of the above is correct

5. Differential RNA synthesis can be demonstrated by
a. in situ hybridization to histological sections
b. Northern blots of RNA from different tissues
c. both of the above are correct
d. none of the above is correct

6. The zona pellucida in mammalian eggs corresponds to the
a. hard shell of chicken eggs
b. hyaline layer of sea urchin eggs
c. perivitelline membrane of sea urchin eggs
d. plasma membrane of sea urchin eggs

7. Embryos of fishes, amphibians, reptiles, and mammals look most similar
a. during cleavage
b. after gastrulation
c. after organogenesis
d. after formation of articulated appendages

8. A mutant allele that is homozygous viable, and recessive to the wild-type allele, is likely to represent
a. a partial loss of function
b. a complete loss of function
c. a gain of function
d. a maternal effect gene

9. Genetic hierarchies are established by
a. monitoring the expression of a given gene in wild-type and various mutant embryos
b. DNase protection assays
c. both of the above are correct
d. none of the above is correct

10. Which of the following is not a cell adhesion molecule?
a. E-cadherin
b. hyaluronic acid
c. N-acetylglucosamine galactosyltransferase
d. N-CAM

EXCHANGE WORDS (2 points per pair)

The following statements are erroneous. However, each one can be corrected by exchanging two single words. Circle these two words within each statement.

11/12. In maternal effect mutants, the genotype of the offspring is determined by the phenotype of the mother.

13/14. The concept of genetic value implies that cells receive information about their coordinates relative to some reference points, and that they interpret their coordinates according to their positional background and previous history.

15/16. Oncogenes are abnormal genes causing cancer because of mutation and/or eukaryotic expression.

17/18. Cytoplasmic transplantation and cell fusion experiments show that gene expression is controlled by the nuclear environment.

19/20. Atavisms are reappearances of phylogenetically older traits in normal development whereas recapitulations are abnormal reappearances of ancient features.

PICK THE ODD STATEMENT (1 point each)

The following are groups of statements. In each group, one statement is correct and three are false, OR three are correct and one is false. Pick the one odd statement, be it false or correct, and circle the respective letter.

21. Self-Assembly
a. Self-assembly is defined as an assembly in which molecules snap together spontaneously.
b. Bacteria self-assemble from DNA and proteins.
c. Microtubules self-assemble from tubulin dimers.
d. Ribosomes self-assemble from their RNA and protein components.

22. Oncogenes
a. Oncogenes are genes causing cancer.
b. Oncogenes can be introduced by viruses or originate directly in eukaryotic cells.
c. Both viral and cellular oncogenes are very similar to normal eukayotic genes called proto oncogenes.
d. The homeotic genes in Drosophila are oncogenes.

23. Genomic Equivalence
a. After mitosis, the two daughter nuclei inherit exactly the same genetic information.
b. There are instances of chromosomal loss during early cleavage divisions.
c. Chromosome elimination (or chromatin diminution) has been observed in the germ line of several animals.
d. There are instances of selective gene amplification in certain cells or tissues.

24. Cell Membrane Proteins
a. Cell membrane proteins are embedded into the phospholipid bilayer of plasma membranes.
b. Collagens are cell membrane proteins.
c. Cell adhesion molecules are cell membrane proteins.
d. Some cell membrane proteins are attached to cytoskeletal elements.

25. Segmentation Genes in Drosophila Embryos
a. Gap genes mutually delimit their expression domains.
b. The expression of gap genes begins after segmentation is complete.
c. Pair rule genes are expressed in two stripes per segment.
d. Segment polarity genes have been discovered as maternal effect mutations.

26. Positional Information
a. According to Wolpert, the cells of an embryonic field receive positional values with respect to certain reference points.
b. Positional values are interpreted by cells according to their genotype.
c. Various positional values may be conferred by a single morphogen.
d. Once specified, positional information may never be changed.

27. Growth Control
a. Hyperplasia is defined as growth by cell division.
b. Most tissues grow strictly by hypertrophy.
c. All growth factors are produced by the pituitary gland.
d. All growth factor receptors are located in the cytoplasm.

28. Regeneration
a. Regeneration always restores the missing parts.
b. Regeneration may cause duplication of the regenerating part.
c. Intercalary regeneration restores the missing intermediates between unlike parts.
d. Misaligned regeneration blastemas may cause supernumerary limb regeneration.

29. Gap Gene Control
a. Gap genes in Drosophila are expressed in patterns of about seven stripes.
b. Gap genes are controlled by segment polarity genes.
c. Gap genes control one another.
d. bicoid+ is a gap gene.

30. Extracellular Matrix (ECM)
a. The composition of ECM is the same everywhere in a given embryo.
b. The composition of ECM is stage-dependent.
c. Pre-migratory neural crest cells cultured on dorsolateral (subepidermal) ECM form dorsal root ganglia.
d. Pre-migratory neural crest cells raised on ECM from the ventral pathway (between somites and neural tube) form pigment cells.

MATCH UP QUESTION (1 point each)

The following is a list of embryological terms (31-40) and their definitions (a-j). Match up by entering the appropriate letters in the spaces behind the numbers.

31. ______ archenteron

32. ______ bindin

33. ______ blastocyst

34. ______ blastopore

35. ______ epiblast

36. ______ epiboly

37. ______ epigenesis

38. ______ gametes

39. ______ ingression

40. ______ polar body

a. early mammalian embryo

b. glycoprotein on acrosomal process of sea urchin sperm

c. haploid sister cell of oocyte

d. migration of cells from surface to interior of embryo

e. opening formed during gastrulation

f. primitive gut

g. progression from simple to complex organization

h. sex cells capable of participating in fertilization

i. spreading movement of epithelial cells to cover deeper embryonic cells

j. upper layer of a bilaminar embryonic disc

41-50. SHORT ESSAY (max. 10 points) Imaginal Discs

Drosophila and other insects with complete metamorphosis have imaginal discs (ID).

A. Describe in general terms when and where IDs are found as well as their eventual fate. Name two examples of ID and their derivatives.
B. What is distinctive about IDs with regard to the hormonal control of metamorphosis?
C. Outline transplantation experiments revealing the determination of ID cells and the limits to the stability of the determined state of ID cells.

51-60. SHORT ESSAY (max. 10 points) Polytene Chromosomes

A. What are polytene chromosomes (PC), and how do they originate?
B. How does the banding pattern of PC originate, and what is its significance.
C. How do puffs (or Babiani rings) of PC originate, and what is the significance of puffs in discovering some of the molecular mechanisms that underlie hormonal control in insect metamorphosis?

61-70. SHORT ESSAY (max. 10 points) Cell Determination

A. Define the three operational criteria used to demonstrate the determined state (or lack thereof) of cells or tissues.
B. How can we model the determined state of cells in terms of mutual transcriptional control among genes?

71-80. SHORT ESSAY (max. 10 points) Synergistic Mechanisms

A. Describe in general terms the principle of synergistic mechanisms in development.
B. Outline two examples.
C. Speculate why synergistic mechanisms may be as frequent as they are.

81-90. SHORT ESSAY (max. 10 points) SRY+ Gene

The segment of the human Y chromosome to which the testis-determining factor (TDF) has been mapped seems to contain only one gene, SRY+.

A. When and where is Sry+, the mouse homologue of SRY+, expressed? Do these data support the hypothesis that Sry+, and by implication SRY+, act as TDF?
B. Which data demonstrate that SRY+ is necessary for male development?
C. Which data show that Sry+ can be sufficient for male development?

91-100. SHORT ESSAY (max. 10 points) Homeotic Genes and Hox Genes

Describe four features that Drosophila homeotic genes and mouse Hox genes have in common. Outline in a few sentences how each feature was discovered.


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