BIO 349 Developmental Biology (K. Kalthoff)

Exams Summer 1994

First Midterm Exam (15 June 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. Centrolecithal cleavage is characteristic of telolecithal and meroblastic eggs, which often contain too much yolk to be cleaved completely.

3/4. Embryonic determination is an interaction between one (inducing) tissue and another (responding) tissue, as a result of which the responding tissue changes its state of induction.

5/6. The first part of sea urchin gastrulation is caused by forces developed within the mesenchymal plate, whereas the last part involves the pulling action of secondary vegetal cells.

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.

7. Genetic totipotency, or at least pluripotency, has been demonstrated in:
a. frog and sea urchin blastomeres
b. nuclei from differentiated frog cells
c. differentiated plant cells
d. all of the above are correct

8. 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

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

10. Anterior determinants in dipteran embryos are thought to be
a. microtubules
b. mitochondria
c. pigment granules
d. ribonucleoprotein (RNP) particles

11. The capacitation of mammalian sperm
a. involves changes in the sperm head
b. occurs in the uterus or oviduct
c. both of the above are correct
d. none of the above is correct

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

13. A male germ line cell after the second meiosis is called a
a. spermatid
b. spermatozoan
c. both of the above may apply
d. none of the above is correct

14. Nurse cells in the egg chambers of insects are
a. diploid
b. haploid
c. both of the above are correct
d. none of the above is correct

15. Which of the following regions of a Xenopus gastrula contribute to the archenteron
a. bottle cells
b. superficial layer of the involuting marginal zone
c. both of the above are correct
d. none of the above is correct

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

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. Cell Determination and Differentiation
a. Cell determination is assayed directly by morphology or histochemistry.
b. Cell determination is stable under any known conditions.
c. Cell differentiation is assayed indirectly by transplantation experiments.
d. Cell differentiation may change during normal development.

18. Regulatory and Mosaic Eggs
a. In mosaic eggs the potency of each blastomere 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.

19. Localized Cytoplasmic Determinants (LCDs)
a. LCDs are always associated with visible markers.
b. Local UV irradiation by itself has proven the existence of LCDs.
c. Heterotopic transplantation can show that an LCD is necessary.
d. A rescue bioassay can be used to characterize the molecular nature of an LCD.

20. Morphogenetic Movements
a. Invagination is the transition of cells from an epithelial layer into an embryonic cavity.
b. Ingression is the flowing of an expanding outer epithelium over the edge of an opening to the inside.
c. Delamination is the splitting of a sheet of cells into two parallel sheets.
d. Convergent extension is the spreading movement of an epithelial sheet to cover a deeper layer of cells.

21-30. SHORT ESSAY (max. 10 points) Role of Bindin in Sea Urchin Fertilization

A. What is bindin?
B. Describe two experiments that have elucidated the location and function of bindin in sea urchin fertilization. Outline experimental techniques, results, and conclusions.

31-40. SHORT ESSAY (max. 10 points) Mitotic Spindle Positioning and Orientation

Describe one genetic and one experimental study that have analyzed the positioning and orientation of meiotic or mitotic spindles in oocytes and blastomeres.

41-50. SHORT ESSAY (max. 10 points) Dorsal Vegetal Blastomeres in Frog Embryo

A. Outline a rescue experiment and a heterotopic transplantation experiment that both demonstrate the role of dorsal vegetal blastomeres in the complete Xenopus embryo. (Note that this question is not asking for the effect of dorsal vegetal blastomeres on isolated animal caps.) Include in your answer the design of the experiments (including controls), the results, and the conclusions drawn.
B. Discuss briefly how the dorsal vegetal blastomeres are thought to acquire their specific activity.

Second Midterm Exam (28 June 1994)

EXCHANGE WORDS (2 points per pair)

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

1/2. In polytene chromosomes from different organs of the same animal, the puffing pattern is virtually constant, whereas the banding pattern may vary considerably.

3/4. Gain-of-function alleles are silent in areas or at stages where the wild-type allele of the same gene is expressed.

5/6. According to the "masked mRNA" hypothesis, mRNA may be kept in an inhibitory state by association with proteins or other untranslatable components.

7/8. Most early embryos synthesize genes while their own proteins are not being transcribed.

9/10. Self-assembly is defined as an assembly process in which only ions of the end product, as well as water and small components, are involved.

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. Which of the following structures is not derived from neural crest cells
a. adrenal medulla
b. basal plate
c. pigment cells
d. sympathetic ganglia

12. The third ventricle of the brain is located in the
a. diencephalon
b. mesencephalon
c. telencephalon
d. none of the above is correct

13. Differential RNA synthesis in certain tissues but not others can be demonstrated by
a. in situ hybridization to histological sections
b. Northern blots to RNA from different tissues
c. both of the above
d. none of the above

14. The parts of nuclear pre-mRNA that eventually become translated are called
a. introns
b. leaders
c. trailers
d. none of the above is correct

15. Mechanisms of translational control include
a. polyadenylation of mRNA
b. longevity of mRNA
c. masking of mRNA
d. all of the above

16. The amino acid sequence of a polypeptide is referred to as its
a. primary structure
b. secondary structure
c. tertiary structure
d. quaternary structure

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.

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. Bicoid (bcd) Gene
a. Embryos from bcd mutant mothers lack thorax and abdomen.
b. The bcd gene is a maternal effect gene.
c. bcd mRNA is localized near the posterior pole of the oocyte as it enters from nurse cells.
d. bcd protein enhances the expression of the Ultrabithorax gene.

19. Protein Synthesis during Spermiogenesis
a. The sperm nucleus is compacted as histone proteins are replaced with protamine.
b. Protamine mRNA has a longer half-life in the developing sperm than most other mRNAs.
c. Protamine mRNA is immediately translated into protamine.
d. The signals for the timing of protamine mRNA breakdown and translation are contained in the trailer region.

20. 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.

21-30. SHORT ESSAY (max. 10 points) Organizer Experiment

A. Describe the organizer experiment of Hans Spemann and Hilde Proescholdt, including
1. the experimental procedure,
2. the results,
3. the major conclusions.

B. How did the age of the donor embryo affect the result of the experiment, and how do you interpret this causal relationship?

31-40. SHORT ESSAY (max. 10 points) Recapitulations and Atavisms

A. Define in general terms recapitulations in development and illustrate the phenomenon with one example.
B. Define in general terms atavisms and illustrate the phenomenon with one example.
C. How might the two phenomena be related?

41-50. SHORT ESSAY (max. 10 points) RNA Splicing in Drosophila Sex Differentiation

A. Outline briefly the cascade of RNA processing steps that control somatic sex differentiation in Drosophila
B. Describe in detail the control of transformer+ (tra+) pre-mRNA splicing by the Sexlethal protein.
C. Support your answer under (2) with evidence.

Final Exam (8 July 1994)

MATCH UP QUESTIONS (1 point each)

The following is a list of key words (1-10) and a list of short descriptions (a-j). Match up by entering the appropriate letters in the spaces behind the numbers.

1. _____ ecdysone

2. _____ field

3. _____ involution

4. _____ nurse cells

5. _____ P element

6. _____ pharyngeal arch

7. _____ polar lobe

8. _____ protamine

9. _____ vitellogenin

10. _____ zona pellucida

a. chromosomal protein in sperm

b. gill rudiment occurring in higher vertebrates

c. groups of cells with size-regulatory properties

d. insect molting hormone

e. morphogenetic movement occurring in gastrulation

f. sister cells of insect oocytes

g. transposable section of DNA

h. transient structure formed during cleavage of molluscs

i. vitelline envelope of mammals

j. yolk protein

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. The marginal cells play a role in the initial phase of amphibian gastrulation whereas later gastrulation is driven by the behavior of deep involuting bottle cells.

13/14. While testis follicles develop in the cortical portion of the gonad, ovarian cords are formed in the medulla.

15/16. The animal pronucleus of an egg is defined by the eccentric position of the female pole and the polar bodies.

17/18. The fast block to polyspermy works by a change in cortical membrane potential while the slow block is part of the plasma reaction.

19/20. A potential is constituted by all cells in an area that have the field of forming a certain organ.

21/22. Many of the evolutionary conditions of mammals do not fulfill a physiological requirement, but reflect their embryonic history.

23/24. During cell division, daughter cells inherit both directed information encoded in DNA andparagenetic information in the form of seed structures for genetic assembly.

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.

25. Mechanisms of translational control include
a. change of intracellular pH
b. masking or unmasking of mRNA
c. polyadenylation or deadenylation of mRNA
d. all of the above

26. Genes for ribosomal (18S + 28S + 5.8S) RNA in amphibian oocytes are
a. amplified selectively
b. repetitive as in other cells
c. both of the above are correct
d. none of the above is correct

27. 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

28. Which of the following techniques is most useful in assaying cell determination?
a. autoradiography
b. cell transplantation
c. Northern blotting
d. Southern blotting

29. In human sexual development, the indifferent stage lasts until the
a. 6th day
b. 6th week
c. 6th month
d. 7th month

30. The male epididymis in mammals is derived from
a. the embryonic kidney
b. the Müllerian duct
c. the urogenital folds
d. none of the above

31. The mammalian sex hormone, testosterone, is produced by
a. interstitial cells (Leydig cells) of the testis
b. ovarian theca cells
c. both of the above are correct
d. none of the above is correct

32. 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

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.

33. Hormones
a. All cells in the body produce the same hormones.
b. Hormones bind to receptors located in the plasma membrane or in the cytoplasm.
c. Many hormones are steroids or peptides.
d. Some hormones control the transcription of certain genes in their target cells.

34. Sex Determination
a. In mammals, sex is determined by the number of X chromosomes.
b. The gene for the testis determining factor (TDF) in mammals is located on the Y chromosome.
c. In the presence of testosterone, the Müllerian ducts develop while the Wolffian ducts degenerate.
d. In Drosophila sex determination is controlled by the environmental temperature.

35. Collagen
a. Collagen self-assembles from tubulin dimers.
b. The procollagen peptides are synthesized within the cytoplasm.
c. Three procollagen peptides form a triple helix.
d. Collagen fibers have important functions in the mitotic spindle.

36. Spermatogenesis
a. Spermatogonia may be connected with each other by cytoplasmic bridges.
b. The axoneme arises from a basal body.
c. The acrosome arises from fused mitochondria.
d. Most of the spermatid cytoplasm is eventually sloughed off.

37. Totipotency
a. Some differentiated plant cells were shown to be totipotent.
b. Mice are cloned routinely by transplanting nuclei from blood cells back into enucleated eggs.
c. Most nuclei from amphibian blastula cells are totipotent.
d. Blastomeres from sea urchin embryos are totipotent until the 4 cell stage.

38. RNA processing
a. Pre-messenger RNA is always shorter than messenger RNA (mRNA).
b. During splicing, each donor site cooperates with the acceptor site of the same intron.
c. The polyadenylation signal is located in an intron.
d. The `cap' of mRNA consists of a modified guanosine.

39. The Barr body (BB)
a. The BB represents an extra nucleolus.
b. The BB is observed in male mammals.
c. The BB is also observed in primordial germ cells.
d. The BB is an example for gene inactivation by a change in chromosome conformation.

40. Steroid Hormones
a. Steroid hormones accumulate in their target organs.
b. Most steroid hormones bind to receptors in the cell plasma membrane.
c. Steroid hormone receptors are transcription factors.
d. Ecdysone is a steroid hormone.

41-50. SHORT ESSAY (max. 10 points) Synergistic Mechanisms

A. State the general principle of synergistic mechanisms.
B. Describe two examples that illustrate the principle.

51-60. SHORT ESSAY (max. 10 points) Convergent Extension

A. Define the morphogenetic movement called convergent extension. Include in your definition the relevant behavior(s) of epithelial cells and the resulting change in overall shape of the epithelium.
B. Describe how the role of convergent extension was demonstrated in amphibian gastrulation and in amphibian neurulation.

61-70. SHORT ESSAY (max. 10 points) Transdetermination

A. Outline the serial transplantation experiment with Drosophila imaginal discs that revealed the ability of cells to undergo transdetermination.
B. Diagram a control circuit consisting of two genes that regulate each other so that two stable states are possible (bistable control circuit).
C. Explain the transdetermination phenomenon in terms of bistable control circuits as described under (2).

71-80. SHORT ESSAY (max. 10 points) Bicoid mRNA as a Localized Cytoplasmic Determinant

A. Define in general terms two operational criteria that are used to demonstrate the action of a localized cytoplasmic determinant.
B. Describe actual experiments that use the criteria defined under (1) and prove that bicoid mRNA acts as an anterior determinant in Drosophila eggs.

NOTE: The correct answer does not entail the molecular mechanism by which bicoid protein controls embryonic hunchback+ expression.

81-90. SHORT ESSAY (max. 10 points) Compartment Hypothesis

A. Describe how clonal analysis led to the discovery of compartments in insect epidermis, and state the general definition of compartments based on this discovery.
B. How does the compartment hypothesis link compartments to the activity of certain genes?
C. Describe evidence that supports the compartment hypothesis.

91-100. SHORT ESSAY (max. 10 points) Pair-Rule Genes

A. Characterize pair-rule genes by their mutant phenotypes and their expression patterns.
B. Name two pair rule genes.
C. How do other genes control the expression of pair-rule genes?
D. Support your answer under (3) with evidence.


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