Download Biology (Bio 315) S

Biology (Bio 315) S. Steiner Examination #2 Fall 1997
If there is more than 1 answer choose the best answer.
1. As we discussed in lecture artificial chromosomes are being synthesized. If you
wanted to make a chromosome which of the following chromosomal elements would
you not need to have a self-replicating chromosome?
A. telomere
B. Centromere
C. Intron DNA*
D. DNA replication origin
E. all of the above are needed for a self replicating Chromosome
2. The feature of histones that allows them to bind tightly to the DNA is (choose the
best answer as there may be more than one correct answer):
A. hydrogen bonding
B. disulfide bridges
C. positively charged amino acids such as arginine and lysine*
D. negatively charged amino acids such as glutamic acid and aspartic acid
E. the three diminsional configuration of the histone protein
3. Which of the following histones is not part of the nucleosome?
A. H1*
B. H2A
C. H2B
D. H3
E. all of the above are part of the nucleosome
4. Which of the following proteins (where the arrow is pointing) is most likely to be
represented in the figure below (choose the best answer- based on the figures in your
text, )?
A. H1 histone
B. DNA polymerase
C. RNA polymerase
D. helix loop helix*
E. none of the above
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5. p53 is thought to be associated with approximately 50% of human cancers and is
thought to involve DNA repair. Recently, a closely related gene, _______, has been
described.
A. p21
B. p73*
C. p54
D. p98
E. none of the above
6. The figure indicated below depicts:
A. DNA synthesis (DNA replication)
B. RNA synthesis (transcription)
C. S-phase of the cell cycle
D. DNA repair
E. None of the above
7. The chromosome shown below differs from an interphase chromosome in that the
interphase chromosome:
A. lacks a centromere
B. has one-half the amount of DNA
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C. lacks a telomere
D. has twice the amount of DNA*
E. none of the above distinguishes between a metaphase and an interphase
chromosome.
8. Although DNA
synthesis in eucaryotic cells
and procaryotic
cells is similar there are
differences. Which
of the following represents a
difference in DNA
synthesis between eucaryotic
and procaryotic cells?
A. the presence of DNA helicase to unwind the DNA
B. the presence of single-stranded DNA binding proteins
C. the use of DNA primase to initiate primer synthesis
D. the presence of different DNA polymerases for the leading and lagging
strands*
E. None of the above represent a difference between eucaryotic and procaryotic
DNA synthesis-
9. Active chromatin is biochemically distinct from inactive chromatin. Which of the
following characteristics does not distinguish active from inactive chromatin?
A. H1 histone is less tightly bound
B. nucleosome histones are highly acetylated on specific lysine residues
C. the nucleosomal histone H2B appears to be less phosphorylated in active
chromatin than in inactive chromatin
D. Active chromatin is enriched in a minor variant from of histone H2A that is
found in many species including Drosophila and humans
E. all of the above are found in active chromatin as compared to inactive
chromatin*
10. The figure below shows one possible mechanism to explain (choose the best
answer as there may be more than 1 answer):
A. how the initiation of DNA synthesis occurs in double stranded DNA
B. how the initiation of transcription occurs in double stranded DNA
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C. how the cell makes sure that each region of the DNA is replicated only once*
D. how the cell targets repair enzymes
E. None of the above
11. A major reason
that the telomere
needs to be
lengthened is
(choose the best
answer)
A. because it
is a “hot spot for
mutation” and therefore there needs to be repair and lengthening
B. the ends of chromosomes tend to be removed by nucleases typically present
in the cell.
C. there is typically shortening within the junk DNA of the chromosome and the
mechanism for coping with the shortening is by adding back the DNA to the telomere
D. the primer prevents replication of the portion of the DNA to which it (the
primer) binds.*
E. none of the above represent a major reason that the telomere needs to be
lengthened.
12. Which of the following is the initiation factor in the initiation of RNA polymerase
activity in bacteria?
A. α (alpha)
B. β (beta)
C. β’ (beta primed)
D. σ (sigma)*
E. ω (omega)
13. The figure below represents a step in:
A. excision repair of DNA
B. formation of a ribosome
C. addition of polyA tail
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D. splicing*
E. Transcriptional regulation
14. Only the mature
mRNA and not the
primary transcript can
exit from the nucleus. The current thinking on how it exits was discussed in class. The
thinking is that it exits (again choose the best answer as there may be more than one
answer):
A. via exit signals on proteins bound to the mRNA*
B. via the polyA of the mRNA
C. via the 5' cap site
D. via the AUG start of the open reading frame
E. none of the above is the correct answer
15. With regard to ribosomes the 28S RNA represents:
A. the major RNA of the large subunit of the ribosome*
B. the major RNA of the small subunit of the ribosome
C. the precursor RNA from which the RNA of the large and small ribosomal
subunits is derived.
D. The RNA associated with transfer RNA
E. None of the above is correct
16. The structure indicated below represents the _________ motif of regulatory
protein.
A. helix loop helix
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B. helix turn helix
C. zinc finger*
D. leucine zipper
E. none of the above
17. The structure below represents which of the above?
A.
B. C. D.*
E.
18. MyoD is a helix loop
protein that is most
helix type of regulatory
active when it (myoD)
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dimerizes (forms a dimer) with:
A. Id
B. AP1*
C. Myod (itself)
D. cap regulatory protein
E. none of the above
19. Which of the above serves to inactivate MyoD.
A.* B. C. D. E.
20. The assay shown below is primarily used to:
A. size fractionate DNA
B. size fractionate RNA
C. size fractionate proteins
D. identify RNA bound to DNA
E. identify proteins bound to DNA*
21. Which of the
following
statements about
regulation of the the lac operon is not accurate?
A. the lac operon contains both genes and regulatory elements
B. the activation of the lac operon by CAP is an example of positive regulation
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C. the activation of the lac operon by the addition of lactose is also an example
of positive regulation*
D. the lac operon will only be turned on under conditions in which lactose is
present and glucose is not
E. all of the above statements are accurate.
22. Eucaryotic RNA polmerases cannot initiate transcription on their own thus they
require a set of proteins called general transcription factors. For transcription of
polymerase II (essentially the only transcription we discussed in class) the first of these
proteins binds to the nucleotide sequence (consensus sequence):
A. AUG
B. poly A
C. TATAA*
D. GCGCGC
E. none of the above.
23. In the early days of undestanding how transcriptional regulatory units (these are not
the site of general transcription factor binding but rather enhancers or repressors)
function it was puzzling how transcription was regulated by DNA elements (places to
which transcriptional regulatory proteins bind) thousands of nucleotides away from the
transcriptional start site. It was finally realized that these distant elements functioned:
A. by looping over to be near the transcriptional start site.*
B. by concentrating the transcription regulatory proteins at high enough
concentration at these sites so that these proteins are able to initiate (or repress)
transcription from a distance.
C. by mediating condensation of the DNA between the transcriptional regulatory
region and the transcriptional start site and thereby actually dramatically decreasing
the distance.
D. by activating excision/insertion enzymes that actually move the
transcriptional regulatory DNA closer to the transcriptional start site.
E. none of the above is the correct answer.
24. Which of the following mechanisms for regulating the activity of gene regulatory
proteins most specifically describes the general way in which steroid hormones
function?
A. by protein synthesis and protein degradation
B. protein phosphorylation
C. addition of a second subunit
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D. stimulation of nuclear entry by removal of an inhibitory protein that otherwise
keeps the regulatory protein from entering the nucleus*
E. none of the above
25. Which of the following statements about nucleosome histones is not accurate?
Nucleosome histones:
A. do not present a serious obstacle to RNA polymerase activity
B. do not present a serious obstacle to DNA replication
C. do not present a serious obstacle to DNA replication because they are rapidly
broken down by specialized histone proteases before the start of DNA replication and
replaced (by transcription and translation) before DNA replication is completed
D. do not present a serious obstacle to RNA polmerase activity because they
“move out of the way”.
E. all of the above statements are accurate
26. In lecture we discussed the fact that men who had testicular cancer are at relatively
high risk of leukemia. The basis for this is:
A. the mutation that results in leukemia and the one that leads to testicular
cancer are the same
B. the treatment for testicular cancer leads to leukemia*
C. testicular cancer has a high rate of metastasis (spread) to the blood system
D. the article was an example of how statistics actually can give a wrong
impression and that in fact there is not a relationship between the two cancers.
27. A new study indicated that the transplantation of animal organs (e.g., pig organs)
into humans likely will present a problem in that:
A. the pig organ is rejected much more rapidly than had previously been
considered
B. the pig organ might contain viruses capable of infected humans*
C. pig organs do not function as well in humans as was originally thought
D. animal rights activists can block the use of animal organs almost indefinitely
E. none of the above are correct
28. Which of the following nucleic acids typically gets methylated in DNA?
A. Guanine
B. cytosine*
C. adenine
D. thymidine
E. 5-azacytidine
29. With regard to transcription which of the following statements is accurate:
A. transcription is most active during mitosis
B. An initial decondensation step is thought to be required before mammalian
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genes can be transcribed.*
C. transcription only occurs in condensed DNA
D. a relatively large proportion of human DNA gets transcribed
E. none of the above statements are accurate
30. The diagram below was used to demonstrate a possible mechanism for (choose
the best answer as there may be more than one answer) :
A. promoter activation
B. promoter suppression
C. amplification by promoter activation
D. creation of cell memory*
E. none of the above
31. Although the way in
which embryonic cells
are differentiated into
different organs is not
clearly understood. One
hypothesis suggests that
the regulation might be
controlled by
___________ .
A. ion concentration in the uterus
B. the level of glucose in the uterus
C. the position of the cells in the embryo*
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D. specialized growth factors provided by the mother via the placenta
E. none of the above
32. X chromosome inactivation contributed significantly to our understanding of the
origins of cancer. The contribution was:
A. that the breast cancer gene is carried on the X chromosome and cells that
carry the gene on condensed X chromosome do not become cancerous
B. that improper X chromosome inactivation results in uncontrolled growth which
eventually leads to cancer
C. that improper X chromosome inactivation results in the loss of function of p53
tumor suppressor gene
D. that most tumors are initiated by a single cancer cell rather than a group of
cancer cells*
E. none of the above
33. DNA methylation is thought to:
A. contribute to the constitutive (on all the time) activity of housekeeping genes
B. contribute to the specificity of protein binding for transcriptional activation
C. contribute to DNA condensation
D. contribute to the turning off genes*
E. none of the above.
34. The following figure is an example of __________:
A.
negative control
of alternative
splicing
B. positive conrol of alternative splicing*
C. positive control of transcriptional activation
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D. negative control of transcriptional activation
E. None of the above
35. Treatment of fibroblasts with 5-azacytodine (5-AZA) results in some of the
fibroblasts being converted to muscle cells, or bone cells. The reason for this is that 5AZA:
A. removes methyl groups from the DNA of regulatory regions of
developmentally regulated genes which results in the activation of their transcription.*
B. adds methyl groups to the DNA of regulatory regions of developmentally
regulated genes which results in the activation of their transcription.
C. produces a high mutation rate in regulatory regions of developmentally
regulated genes leading to activation of those genes.
D. Modifies proteins that are involved in activating developmentally regulated
genes.
E. none of the above explain how 5-AZA converts fibroblastic cells to muscle
cells
36. Alternative splicing produces a cell type specific form of _________ gene product
seen below.
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A.
B.
C.
D.
E.
elongation factor protein
p53 protein
steroid hormone receptor
Src protein*
None of the above
37. An important difference in eucaryotic and procaryotic translation, aside from
capping and the Shine-Delgarno sequences, that relates to why most if not all
eucaryotic messages are able to code for only 1 protein is:
A. eucaryotic ribosomes dissociate rapidly from mRNA when translation
terminates*
B. eucaryotic messages typically contain only a single AUG
C. eucaryotic messages are much longer than procaryotic messages
D. eucaryotic ribosomes contain blocking proteins which prevent the initiation of
translation of a second protein from the same mRNA.
38. mRNA often contains nucleotides that are upstream of the AUG start site. These
nucleotides (termed as 5' untranslated region):
A. have no known function
B. are cleaved prior to translation
C. have been shown to contain protein binding sites required to complete
transcription
D. have been shown to contain protein binding sites that block translation of
some proteins *
39. The best (best in the sense of indicating the most important point of the figure)
explanation for the figure below is:
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A. initiation factor is need for protein synthesis
B. the phosphorylation of an initiation factor regulates protein synthesis*
C. guanine releasing protein releases GDP from the initiation factor thereby
making it inactive
D. GTP is required for protein synthesis
E. GDP is required for protein synthesis
40. Similar to the situation at the 5' end there are also nucleotides at the 3' end of the
mRNA that are downstream of the coding region (that is, 3' untranslated region).
Although there are likely a number of important functions for these nucleotides one
important function that we discussed is to:
A. assure stable translation
B. contribute to the stability of the mRNA*
C. contribute to the stability of the ribosome
D. act as the docking site for the stop codon
E. none of the above represents an important function of the 3' untranslated
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region of the mRNA.
41. Membrane phospholipids are assymetrically assembled in the surface membrane
and _________ is almost exclusively associated with the inner leaflet of the surface
membrane (cytoplasmic surface) (choose the best answer).
A. phosphatidylethanolamine
B. phosphotidylcholine
C. sphingomyelin
D. phosphatidylserine *
E. none of the above phospholipids is associated with the inner leaflet of the
surface membrane
42. Which of the following lipids gives elasticity to red blood cells (choose the best
answer)?
A. glycolipids
B. sphingomyelin
C. phosphatidylcholine
D. cholesterol*
E. phosphatidylinositol
43. Which of the above lipids has been shown to act as an anchor for proteins?
A. B. C. D. E.*
44. One relatively easy way to determine whether or not a membrane associated
protein is peripheral (as compared to being integral) is to determine whether or not its
removal from the membrane can be accomplished by use of:
A. detergent
B. organic solvents
C. salt solution*
D. enzymatic digestion
E. none of the above will distinguish between integral and peripheral membrane
proteins
45. The technique known as fluroescent recovery after photobleaching (FRAP) is used
to:
A. determine the distribution of specific phospholipids between inner and outer
leaflets of the plasma membrane.
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B. determine the nature of the carbohydrate layer on the outer surface of the
plasma membrane
C. Determine the lateral mobility of surface membrane proteins*
D. determine the lateral diffusion rate of lipids
46. Most of the carbohydrate chains (oligosaccharides) associated with surface
membrane proteins are attached to :
A. serine
B. tyrosine
C. threonine
D. asparagine*
E. arginine
47. The transport of glucose from the lumen of the gut to the inside of the intestinal
epithelial cell is an example of:
A. antiport transport
B. uniport transport
C. aqueous channel transport
D. symport transport*
E. none of the above
48. Proteins purified from the mitochondrial matrix were smaller than would have been
predicted based on the nucleotide sequence of the open reading frame (AUG start to
Stop codon). The reason for this is that (choose the best answer):
A. mitchondrial protein mRNA is unusual in that the coding reading starts at the
second AUG making it appear as thought the protein was smaller than it should have
been. Thus, the protein size of the mitochondrial proteins was overestimated.
B. At the time of the above studies it was not realized that there was a 5'
untranslated region in the mRNA’s of mitochondrial proteins. Thus, the protein size of
the mitochondrial proteins was overestimated.
C. Mitochondrial proteins are alternatively spliced variants of cytosolic proteins
and the mitochondrial proteins have a small intron removed which makes them smaller
than one would predict based on the mRNA.
D. mitochondrial proteins contain a signal peptide which is cleaved when the
protein enters the mitochondrion.*
E. none of the above are accurate.
49. Current thinking on the role of the mitochondrion in disease suggests that the
release of proteins from mitochondria triggers cell death via apoptosis. The proteins are
thought to be released by (choose the best answer):
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A. overactive electron transport chain
B. damage of the mitochondrial protein receptor protein
C. depolarization of the mitochondrial inner membrane due to uptake of excess
calcium into the mitochondrion*
D. defects in the hsp 70 helper proteins
E. none of the above
50. Which of the following statements about the nucleus is not accurate?
A. the initial stage of protein import into the nucleus (i.e., targeting) requires
ATP*
B. proteins destined to enter the nucleus are brought to the nucear pore by
cytoplasmic helper factors (ie., nucleoporins).
C. breakdown of the nuclear envelope during mitosis involves phosphorylation of
nuclear lamins
D. the outer nuclear membrane is considered as an extension of the
endoplasmic reticulum
E. All of the above statements are accurate (if you believe that all of the above
statements are accurate choose this answer).
51. The distance between inner and outer mitochondrial membranes is greater than the
length of most mitochondrial matrix proteins. Given that fact how do mitochondrial
proteins traverse the intermembraneous space (choose the best answer)?
A. they are carried through the region by hsp70 proteins
B. there are contact sites in the mitochondrion through which proteins pass
C. Most mitochondrial proteins in the matrix are made by mitochondrial DNA and
do not need to pass through the intermembrane space
D. they can change their three-dimensional conformation from hydrophobic (to
get through the outer membrane) to hydrophilic (to diffuse throught the intermembrane
space) and back to hydrophobic to get throught the inner mitochondrial membrane.
E. none of the above are correct.
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