BioC6011 EXAM 4 DECEMBER 7, 2007
1. What is micro RNA?
a) Micro RNA is synonymous with the genome of RNA retroviruses
b) Micro RNA is a small, non-coding RNA encoded in the genomes of eukaryotes *
c) Micro RNA is the smallest of the small nucleolar RNAs that assist in rRNA
processing
d) Micro RNA is a name for all polycistronic transcript in prokaryotes
e) None of the above
2. How do prokaryotes regulate different genes that encode enzymes, which are required in
the same biosynthetic pathway?
a) Multiple genes can be under the control of the same promoter. This is called an
operon. *
b) Multiple genes are under the control of individual promoters but they are all
transcribed at precisely the same time.
c) They form an operon with individual promoters, but one single repressor region.
d) They form an operon with one single repressor region, but multiple individual
promoters.
e) None of the above
3. Promoters lie ________ of the +1 transcription start site
a) upstream *
b) downstream
c) midstream
d) none of the above
e) all of the above
4. What is a promoter?
a) The binding site for transcription factors.
b) The binding site for repressors.
c) The binding site for ribosomes.
d) The binding site for RNA polymerase. *
e) None of the above
5. What is a repressor?
a) A regulator that affects translation negatively.
b) A regulator that affects translation positively.
c) A regulator that affects transcription positively.
d) A regulator that affects transcription negatively. *
e) None of the above
6. Can repressors ever turn into activators?
a) No, never.
b) Yes, all represssors can find a binding partner that turns them into activators.
c) Yes, in mammalian cells, some repressors can become activators. *
d) Yes, in prokaryotes all repressors also function as activators.
e) None of the above
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7. What do eukaryotes have that prokaryotes don’t have?
a) Promoters
b) Enhancers
c) Repressors
d) Introns *
8. What do prokaryotes have that eukaryotes don’t have?
a) Ribosomes
b) Replication origins
c) Self-splicing
d) Operons *
9. Nuclear hormone receptors that are inactive in the absence of ligand are
a) located in the cytoplasm as homodimers *
b) located in the nucleoplasm as homodimers
c) located in the cytoplasm as heterodimers
d) located in the nucleoplasm as heterodimers
e) None of the above
10. In eukaryotic genomes, enhancers can reside where? Which one of the following
statements is CORRECT?
a) Inside of introns *
b) Inside of promoters
c) Always upstream of +1
d) Always downstream of +1
e) Only in exons
11. Activation domains in transcription factors recruit what type of proteins?
a) Histone deacetylases
b) Histone kinases
c) Histone acetyltransferases *
d) Histone ubiquitinating enzymes
e) None of the above
12. How can you identify introns?
a) Exon/Intron junctions are conserved. *
b) Exon/Intron junctions are unique for every gene.
c) Exon/Intron junction are highly variable in sequence, because otherwise
alternative splicing wouldn’t exist.
d) Exon/intron junctions in eukaryotes are the same as in prokaryotes.
13. What
a)
b)
c)
is the purpose of alternative splicing?
It’s a safety net against errors in splicing.
It’s a method to turn an intron into an exon.
It’s a mechanism by which an exon can be spliced out to create higher protein
variability. *
d) It’s useless, but doesn’t bother the cell.
14. What
a)
b)
c)
d)
type of RNA catalyzes splicing?
mRNA
tRNA
rRNA
snRNA *
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15. Which of the following statements about ubiquitin is INCORRECT?
a) Ubiquitin can form ubiquitin chains
b) Ubiquitin is a peptide
c) Ubiquitin plays a role in cell cycle regulation
d) Ubiquitin is a phospholipids *
e) Ubiquitination requires E1, E2, E3 enzymes
16.
The half-life of a protein depends on
a) 5’ decapping
b) 3’ deadenylation
c) the N-terminal amino acid *
d) the C-terminal amino acid
e) none of the above
17. The proteasome is involved in the degradation of
a) DNA
b) RNA
c) Proteins *
d) a+b
e) b+c
18. Why is p53 first produced and then degraded in normal cells?
a) Cells are stupid, it’s all a waste of energy
b) It isn’t degraded in normal cells
c) It isn’t transcribed and translated in normal cells
d) To have some p53 present, just in the event of DNA damage *
e) None of the above
19. Which of the following modifications is often required for the activation of transcription
factors?
a) Methylation
b) Ubiquitination
c) Transformation
d) Phosphorylation *
20. Some antibiotics target specifically prokaryotic ribosomes. How do ribosomes differ in
bacteria and eukaryotes?
a) Only in the small subunit, the large subunit is the same
b) Only in the large subunit, the small subunit is the same
c) They differ in both small and large subunits, and the prokaryotic large subunit is
called 80S
d) They differ in both small and large subunits, and the eukaryotic large subunit is
called 60S *
e) None of the above
21. A tRNA with the anticodon 5’ UAG 3’ recognizes which of the following codons?
a) 5’ UAG 3’
b) 5’ TAG 3’
c) 5’ CUA 3’ *
d) 5’ CTA 3’
e) none of the above
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22. How is eukaryotic mRNA recruited to the ribosome?
a) It isn’t, it’s a hit or miss process
b) Ribosomal subunits assemble onto pre-mRNA as it is transcribed in the nucleus
c) Specialized m-RNA transporter proteins connect the large ribosomal subunit with
the m-RNA
d) Ribosomal initiation factors recognize the 5’ cap in mRNA *
e) None of the above
23. Which of the following is an RNA degradation pathway?
a) RNA editing
b) RNA silencing by miRNA
c) Nonsense mediated decay
d) a+b
e) b+c *
24. You’re a ribosome. You’re translating an open reading frame of 100 codons, including
the START and STOP codons. How long is the polypeptide you’re making?
a) 99 amino acids *
b) 100 amino acids
c) 101 amino acids
d) either a or b
e) None of the above
25. What’s the first amino acid in your polypeptide?
a) Nothing special, it could be anything
b) Proline
c) Tryptophan
d) Methionine *
e) None of the above
26. The first tRNA starting the translation process is always positioned over the ____ in the
ribosome.
a) A site
b) B site
c) E site
f) P site *
g) None of the above
27. The universal code has ____ codons (including STOP codons)
a) 36
b) 42
c) 51
d) 64 *
e) 79
28. What
a)
b)
c)
d)
e)
happens inside the endoplasmic reticulum?
Not much
RNA processing
Translation
Protein folding *
None of the above
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29. To make a cDNA library, you need to
a) reverse transcribe genes
b) reverse transcribe mRNA *
c) utilize PCR
d) do a microarray experiment
e) none of the above
30. You’ve had enough of dental school (already) and decide to pursue a career in acting.
You join the cast of CSI Miami and a journalist (from people magazine) asks you to explain
the principle of DNA fingerprinting. You answer: “DNA fingerprinting is based on the fact
that we have variable nucleotide random repeats, and that the number of repeats
a) is the same in all individuals.”
b) is the same in all females.”
c) is the same in all males.”
d) is rarely the same in two individuals.” *
e) none of the above
31. Why do you use PCR in DNA fingerprinting?
a) Because the sequence of the region to be amplified is known
b) Because usually there is very little DNA at a crime scene
c) Because the size of the PCR fragment will increase with the number of repeats
d) All of the above *
e) None of the above
32. Which type of enzyme do you employ to make use of a polylinker or multi-cloning site
in a cloning vector?
a) An exonuclease
b) A restriction enzyme *
c) A reverse transcriptase
d) A topoisomerase
e) None of the above
33. You can use microarrays to examine the transcriptional profile of patients. You notice
that in one group of patients a particular gene is always inactive. You suspect that there
might be a mutation either in the gene or its promoter region. You clone the gene and the
promoter region and send the plasmids off to the U of M sequencing facility. What’s the key
reagent that they use to perform the sequencing reactions?
a) Ribonucleotides
b) 2’ deoxyribonucleotides
c) 3’ deoxyribonucleotides
d) 2’, 3’ di-deoxyribonucleotides *
e) none of the above
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34. One of your patients drinks excessive amounts of milk and creates environmental
pockets in his mouth where lactose is the only carbon source. What happens to the bacteria
that live in this micro-environment?
a) Lactose binds to the lac-repressor and increases binding to the operator
b) Lactose binds to the lac-repressor and enables the repressor to bind to the
promoter region
c) Lactose binds to RNA polymerase and enables the polymerase to bind to the
promoter
d) Lactose binds to the lac-repressor and inhibits it from binding to the operator.
This inhibition is enough to drive high-level transcription of the lac-operon.
e) None of the above *
35. Pathogenic bacteria can be taken up and killed by
a) Red blood cells
b) Cytotoxic T cells
c) B-cells
d) Macrophages *
e) None of the above
36. Autoreactive T cells can be removed by apoptosis. Which class of proteins needs to be
cleaved to become active and degrade other cellular factors?
a) perforins
b) Bcl-2 family members
c) caspases *
d) p53
e) all of the above
37. What’s a hallmark of apoptosis?
a) Calcium release from the endoplasmic reticulum
b) Cytochrome c release from mitochondria *
c) Potassium influx into the cytoplasm
d) Sodium excretion through the plasma membrane
e) None of the above
38. What type of cells can be infected by HIV through interaction with the membrane
receptor CD4?
a) Cytotoxic T cells
b) T helper cells *
c) Macrophages
d) Platelets
e) All of the above
39. Bone
a)
b)
c)
d)
e)
marrow transplants can potentially restore a defective
liver
digestive system
heart
immune system *
None of the above
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40. Mario Capecchi received this year’s Nobel Prize in Medicine for developing the gene
knock-out strategy for mammalian cells. Why is this strategy useful?
a) It allows scientists to understand how a gene (or the lack thereof) affects
development and viability of an organism (e.g., of a knock-out mouse).
b) It allows scientists to mimic a naturally occurring gene deletion that causes a
disease and to develop an animal model to study the disease.
c) It allows scientists to take out one copy of a gene in a diploid organism and study
whether lowering the gene number affects development and viability.
d) All of the above *
e) None of the above
41. IgM is always the first Ig isotype that is produced in response to an infection. What’s
unique about IgM?
a) Nothing
b) It has only a single antigen binding site
c) It’s membrane bound *
d) It has only heavy chains
e) none of the above
42. IgA is highly concentrated in the saliva. What’s unique about IgA?
a) It’s a monomer
b) It’s a dimmer *
c) It’s a trimer
d) It’s a tetramer
e) all of the above
43. Multiple Myeloma is a cancer of plasma cells. What are plasma cells?
a) Lymphocytes *
b) Red blood cells
c) Macrophages
d) T helper cells
e) none of the above
44. It’s 2025, your former biochemistry instructor is sitting in your dental chair (scared as
hell). Her chocolate addiction has clearly affected her teeth (unfortunately she’s also
50 pounds overweight) and she’s about to lose her upper left incisor. You’re
recommending “tooth regeneration therapy”, which allows you to implant an in vitro
cultivated root that originated from her own stem cells. What happens during this in
vitro differentiation?
a) The stem cells multiply and never lose their replicative potential.
b) The stem cells first need to be reprogrammed before they can proliferate and
differentiate.
c) Pluripotent stem cells will never develop into roots. They are already
programmed.
d) Root-specific growth hormones facilitate the in vitro differentiation. Cells shut
down their cell cycle genes and start to express root-specific factors. *
e) Nothing, stem cells lose their proliferative potential once they are isolated from an
organism and put into a Petri dish.
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45. How do osteoblasts regulate bone resorption by osteoclasts?
a) They produce anti-osteoclast poison
b) They produce cytokines that inhibit the growth of osteoclasts
c) They inhibit resorption by secreting osteoprotegerin, a decoy receptor *
d) They increase resorption by secreting osteoprotegerin, a decoy receptor
e) None of the above
46. Cyclic AMP is an important second messenger in signal transduction. Which of the
following is also a second messenger?
a) Cyclic TMP
b) Calcium *
c) ATP
d) Vitamin D
e) None of the above
47. Cyclic GMP activates which protein kinase?
a) Protein kinase A
b) Protein kinase B
c) Protein kinase C
d) Protein kinase D
e) None of the above *
48. G protein coupled receptors
a) dimerize upon ligand binding
b) have seven transmembrane alpha-helical domains *
c) have tyrosine residues in the cytoplasmic domain
d) autophosphorylate themselves upon ligand binding
49. Which subunit in trimeric G-proteins binds GDP/GTP?
a) alpha *
b) beta
c) gamma
d) epsilon
e) kappa
50. What do receptor tyrosine kinases and cytokine receptors have in common?
a) Signaling through these receptors requires trimeric G proteins
b) Both are monomeric receptors when bound to ligand
c) Both activate adenylate cyclase to make cAMP
d) Both signal independently of second messengers *
e) none of the above
I had a lot of fun this semester. Good luck to all of you and happy holidays!!!
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