Sections 3, 4H
Dr. Ramin Yadegari
Hour Exam #4
December 1, 2011
(Version 1 KEY)
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1. The predominant mechanism driving cellular differentiation is the difference in gene
2. Which observation below provides evidence that differentiated cells retain all the genes
of developing cells?
a) Developing cells have many mRNA transcripts in common with mRNAs produced in
b) Differentiated cells generally synthesize a specific group of proteins.
c) *Nuclei from mature cells can direct the development of an entire individual.
d) Not all mature cells are capable of differentiation.
e) None of the above.
3. Gene expression in developing organisms is regulated on several different levels. In
many developing animals, regulation of gene expression is influenced by the action of
Hox genes. Which of the following gene products is encoded by Hox genes?
a) *transcription factors
b) cell-surface molecules for cell-cell interactions
c) signal-transduction factors such as protein kinases
d) mRNA-processing factors
e) Protein-degradation factors
1 4. Bicoid mutations produce “two-tailed’ Drosophila embryos. The protein encoded by the
bicoid gene in Drosophila determines the _____ of the embryo.
a) *anterior-posterior axis
b) anterior-lateral axis
c) posterior-dorsal axis
d) posterior-ventral axis
e) dorsal-ventral axis
5. Suppose you purified the protein encoded by the bicoid gene and injected it into the tail
end of an early Drosophila embryo before formation of the head or tail structures. What
might be the result of such an experiment after you allow further development to
a) The embryo would show no development of ventral regions.
b) The embryo would show no development of anterior regions.
c) The embryo would show a head and a tail as normal.
d) The embryo would show two tails.
e) *The embryo would show two heads.
6. All of the following are true of embryonic stem cells except _____.
a) they can be found in human blastocysts
b) they retain the potential to become different types of cells
c) they continue to undergo mitosis when most cells have stopped dividing
d) *they are terminally differentiated
7. What does the ABC model of flower development attempt to explain?
a) *how different combinations of transcription-factor proteins trigger the formation of
different floral organs
b) why petals are colorful whereas the sepals are green
c) why the four types of floral organs occur in whorls
d) why apical meristems are converted to floral meristems in response to specific cell-to-cell
8. Which of the following statements about stem cells is true?
a) Embryonic stem cells can be harvested from human embryos produced during in vitro
b) The only known pluripotent animal stem cells are derived from embryos.
c) The manner in which embryonic stem cells differentiate can be channeled by the
d) Both a and b
e) *Both a and c
9. Induced pluripotent stem cells
a) are obtained via activation of several genes required for the pluripotent character of the
b) may be produced from differentiated cells in culture .
c) can be induced to form many different tissues.
d) *All of the above
e) None of the above.
2 10.Mammalian adult stem cells are usually capable of dividing into a few cell types; they
are therefore said to be _______.
c) terminally differentiated
11.To respond to a signal, a cell must have a(n) _______ molecule that can detect the
e) All of the above
12.The receptor of cortisol
a) is an ion channel receptor.
b) is a protein kinase receptor.
c) exists within the plasma membrane and dimerizes.
d) *can form a complex that binds to DNA.
e) None of the above
13.Which of the following statements about the insulin receptor is false?
a) It autophosphorylates (phosphorylation of its own select amino acid residues).
b) It requires binding by two insulin molecules to be activated.
c) It catalyzes the phosphorylation of insulin response substrates.
d) *It is located entirely within the cytoplasm.
e) None of the above
14.Viagra, used to treat erectile dysfunction, acts by means of the release of the second
a) cyclic AMP.
b) calcium ion.
c) *nitric oxide.
15.The receptors for steroid hormones are located inside the cell, instead of on the
membrane surface like most other signal receptors. Why is this not a problem for
a) because the receptors can be readily stimulated to exit and relocate on the membrane
b) because receptors located inside cells are less susceptible to blockage by inhibitors
located on or near the cell surface, so it serves as a protective mechanism
c) *because steroid hormones are lipid soluble so can readily diffuse through the lipid
bilayer of the cell membrane
d) because the receptors are repressible, meaning they are actively altering cell function
unless the target hormone is present
3 16.Put the steps of the process of signal transduction in the order they occur:
1. A conformational change in the signal-receptor complex activates an enzyme.
2. Protein kinases are activated.
3. A signal molecule binds to a receptor.
4. Target proteins are phosphorylated.
a) 1, 2, 3, 4
b) *3, 1, 2, 4
c) 3, 4, 1, 2
d) 3, 2, 1, 4
17.Plasmodesmata are cell-cell junctions that are found between ___________.
a) individual cardiac cells in heart muscle tissue
b) *adjacent plant cells
c) adjacent animal cells in the same tissue type
d) the plasma membrane of actively dividing prokaryotes
e) None of the above.
18.Hormones are chemical substances produced in one organ that are released into the
bloodstream and affect the function of a target organ. For the target organ to respond
to a particular hormone, it must _____.
a) modify its plasma membrane to alter hormone entering the cytoplasm
b) be from the same cell type as the organ that produced the hormone
c) experiencing an imbalance that disrupts its normal function
d) *have receptors that recognize and bind the hormone molecule
19.What does it mean to say that a signal is transduced?
a) The signal enters the cell directly and binds to a receptor inside.
b) *The physical form of the signal changes between the outside of the cell and the inside.
c) The signal is amplified, such than even a single molecule evokes a large response.
d) The signal triggers a sequence of phosphorylation events inside the cell
20.A G-protein receptor with GTP bound to it _____.
a) *is in its active state
b) signals a protein to maintain its shape and conformation
c) will use cGMP as a second messenger
d) directly affects gene expression
21.Which of the following sequences (in a double-stranded form) is most likely to be cut by
a restriction enzyme?
22.Which of the following is a correct difference between a gene library and a gene clone?
a) *A gene library contains many different cloned DNA sequences; a gene clone contains
one type of DNA sequence.
b) A gene library contains one type of cloned DNA sequence; a gene clone contains many
different DNA sequences.
c) A gene library is a much longer piece of DNA sequence than a gene clone.
d) A gene library is a much shorter piece of DNA sequence than a gene clone.
e) A gene library is sequence information stored in a computerized database; a gene clone is
an actual sequence of DNA.
4 23.Plasmids are used as cloning vectors in genetic engineering. This means that plasmids
allow for _____.
a) *carrying of DNA into a cell and DNA replication
b) DNA to mutate within the gene of interest