Lecture 1-11 Flashcards
(125 cards)
1
Q
Prokaryotic cells are generally smaller than eukaryotic cells and have no membrane-bound organelles, which act to transport some materials around the cell and compartmentalize certain cellular processes. Why do prokaryotic cells not require such membrane-bound organelles?
A
The small size of prokaryotes allows easy diffusion of most molecules, so it is not necessary to compartmentalize activities.
2
Q
Which of the following is a similarity between prokaryotes and eukaryotes?
a. Both share an identical genetic language. b. Both share a common set of membrane-bound organelles. c. Both share some common structural features. d. a and c e. a, b and c
A
d
3
Q
What level of structure in proteins is maintained by interactions between amino acid R groups?
a. quaternary structure b. tertiary structure c. primary structure d. a and b e. a, b, and c
A
d
4
Q
As cells increase in size, ________.
a. the ability of a cell to obtain a sufficient amount of nutrients from the environment is hampered
b. their surface area ∕ volume ratio decreases
c. their surface area ∕ volume ratio increases
d. a and b
e. a and c
A
d
5
Q
The most abundant type of macromolecule (based on total mass) in a typical cell is:
a. water b. carbohydrate c. lipid d. protein e. deoxyribonucleic acids
A
d
6
Q
Which of the following is a nucleotide?
a. phosphate + ribose b. adenine + deoxyribose c. sugar + nitrogenous base d. adenine + ribose + phosphate e. b and c
A
d
7
Q
Which statement about carbohydrates is NOT correct?
a. Starch is a storage form of carbohydrates that can be found within animal cells.
b. Cellulose is a polysaccharide that is not digestible by humans.
c. Monosaccharides are the building blocks of complex carbohydrates within cells.
d. Certain carbohydrates can be used to protect the outer surface of the cell.
e. Carbohydrates are metabolized to provide energy for other cellular processes.
A
a
8
Q
Which of the following possess all properties of life?
a. A yeast
b. A protozoan (a single-celled eukaryote)
c. A virus
d. Two of the above
e. All of the above
A
d
9
Q
The third tenet of cell theory, proposed by Rudolf Virchow states:
a. All organisms are comprised of one or more cells.
b. All cells arise from division of pre-existing cells.
c. Cells are the structural units of life.
d. Cells must be small to facilitate uptake of nutrients and removal of wastes.
e. Cells must be able to respond to external stimuli.
A
b
10
Q
Which statement is NOT correct about proteins of cells?
a. Polypeptides can join together using non-covalent bonds to create a quaternary protein structure.
b. Beta helices and alpha sheets are examples of protein secondary structures.
c. Some proteins act as enzymes to accelerate chemical reactions within the cell.
d. Hydrophobic residues are found in a protein’s inner core.
e. Disulphide bridges can help create the tertiary structure of a protein.
A
b
11
Q
You are carrying out experiments in cell fusion by fusing together cells at different stages of the cell cycle. You then observe the behavior of each nucleus residing in the combined cytoplasm of the two cells. Which of the following responses would occur if you fused a G1 cell to a cell in the S phase?
a. The nucleus from the G1 cell started to replicate its DNA.
b. The G1 nucleus did not initiate DNA synthesis, but the S phase nucleus continued
replication.
c. The S phase nucleus ceased replication.
d. a and c
e. The G1 nucleus did not initiate DNA synthesis, and the S phase nucleus stopped replication.
A
a
12
Q
When cyclin concentration is low, _____________.
a. the kinase of MPF lacks the cyclin subunit and is thus inactive b. the kinase of MPF lacks the cyclin subunit and is thus active c. MPF activity is high and the cell enters M phase d. MPF activity is low and the cell stays in G2 phase e. a and d
A
e
13
Q
What conclusions have been drawn about the functioning of the maturation-promoting factor?
a. Progression of cells into mitosis depends on an enzyme whose main activity is to phosphorylate other proteins. b. MPF activity is controlled by a subunit whose concentration varies from one cell cycle stage to another. c. The activity of a cyclin is controlled by maturation-promoting factor. d. a and b e. a, b, and c
A
e
14
Q
What would be likely to happen to cultured cells if you were able to treat them with an inhibitor that specifically depressed the activity of wee1 kinase?
a. Cdk would be activated earlier than usual. b. Cdk activity would be turned off. c. The cells would be driven from G2 to mitosis. d. a and c e. b and c
A
d
15
Q
What enzyme attaches a chain of proteins to other proteins that have been targeted for degradation, thus ensuring their destruction?
a. ubiquitinase b. protease c. ubiquitin ligase d. kinase ligase e. ubiquitin kinase
A
c
16
Q
A(n) __________ cell typically has a cell cycle lasting 30 minutes, whereas a(n) _______ cell can have a cell cycle lasting several months.
a. early embryo; liver cell
b. red blood cell; early embryo
c. red blood cell; liver cell
d. early embryo; red blood cell
e. liver cell; nerve cell
A
a
17
Q
Which of the following is/are correct about centrosomes?
a. They are microtubule organizing centers.
b. Centrosomes move apart during mitosis due to the polar microtubules pushing against each other through the action of kinesins.
c. The ‘plus (+) ends’ of the microtubules are found near the centrosomes.
d. a and b
e. a, b, and c
A
d
18
Q
Which of the following is NOT true about MPF?
a. The Wee-1 protein inhibits MPF by attaching a phosphate to a tyrosine residue on the kinase subunit of MPF.
b. MPF promotes the condensation of DNA by acetylating histone proteins.
c. MPF is a complex of two proteins, a cyclin and a kinase.
d. When activated, MPF helps initiate the assembly of the mitotic spindle.
e. MPF can inhibit its own functions by activating another protein that will promote MPF destruction.
A
b
19
Q
Place the following events in one of the arrest pathways in the correct order starting with a G2 cell detecting the presence of DNA damage caused by ionizing irradiation.
1 - The cell is stuck in G2.
2 - Chk2 phosphorylates p53 protein
3 – The p21 protein binds to Cdk to inhibit it
4 – ATM kinase is activated and phosphorylates a checkpoint kinase, called Chk2.
5 - The p53 molecule activates transcription of the p21 gene
6 – ATM protein detects DNA damage
a. 2 – 4 – 5 – 3 – 1 - 6
b. 6 – 4 – 5 – 2 – 3 - 1
c. 6 – 2 – 4 – 5 – 3 - 1
d. 6 – 4 – 2 – 5 – 3 - 1
e. 6 – 4 – 2 – 1 – 5 – 3
A
d
20
Q
Microtubule elongation and shortening while chromosomes are being moved to the center of the dividing cell are the result of the _____ and ______, respectively, of subunits at the _____ end of the microtubules.
a. gain, loss, minus b. gain, loss, plus c. loss, gain, plus d. loss, gain, minus e. gain, gain, plus
A
b
21
Q
Cells that have stopped dividing and are arrested in a stage preceding the initiation of DNA synthesis are said to be in a ______ state.
a. G1 phase b. S phase c. G2 phase d. M phase e. G0 phase
A
e
22
Q
The site on DNA to which RNA polymerases bind before initiating transcription is called the
a. terminator b. operator c. promoter d. enhancer e. silencer
A
c
23
Q
Proteins that help RNA polymerase recognize promoters are called __________.
a. transcription factors b. translation factors c. elongation factors d. proteases e. a and c
A
a
24
Q
Large molecular weight RNAs that are restricted to the nucleus and that have diverse nucleotide sequences are called __________.
a. mRNAs b. homogeneous nuclear RNAs c. heterogeneous nuclear RNAs d. hnRNAs e. c and d
A
e
25
The 3' end of most eukaryotic mRNAs contains a ______, while the 5' end has a _________.
a. poly(A) tail, methylated guanosine cap
b. poly(U) tail, methylated guanosine cap
c. methylated guanosine cap, poly(A) tail
d. poly(A) tail, sulfonated guanosine cap
e. methylated guanosine cap, poly(U) tail
a
26
What is the name of the enzyme that adds the poly(A) tail to a messenger RNA?
a. poly(A) endonuclease
b. poly(A) exonuclease
c. poly(A) polymerase
d. RNA polymerase II
e. RNA polymerase III
c
27
What is the function of the poly(A) tail on most mRNAs?
a. to hasten degradation of the mRNA
b. to prevent premature degradation of the mRNA by exonucleases
c. to prevent premature degradation of the mRNA by endonucleases
d. to prevent viral infections
e. to decrease the stability of mRNA
b
28
General transcription factors bind to the _______, while the glucocorticoid receptor binds to the _________.
a. distal promoter; glucocorticoid response element
b. GC and CAAT boxes; distal promoter
c. TATA box; GC and CAAT boxes
d. proximal promoter; core promoter
e. enhancer; core promoter
b
29
The removal of introns from hnRNA is mediated by
a. small nucleolar ribonuclear proteins (snoRNPs)
b. polyribosomes
c. spliceosomes
d. exonucleases
e. RNA polymerase
c
30
What is the name of the molecular machine that translates the code stored in mRNAs?
a. lysosomes
b. endosomes
c. ribosomes
d. ribotomes
e. microsomes
c
31
Ribosomes are made of _______.
a. proteins
b. lipids
c. tRNA
d. rRNA
e. a and d
e
32
Which RNAs owe their activity to their complex secondary and tertiary structures?
a. tRNAs
b. rRNAs
c. mRNAs
d. a and b
e. a, b and c
d
33
What is the major determinant of RNA folding?
a. hydrophobic interactions
b. van der Waals forces
c. ionic bonds
d. formation of complementary base pair regions
e. hydroponic interactions
d
34
Which eukaryotic RNA polymerase synthesizes the larger rRNAs, like 28S, 18S and 5.8S rRNAs?
a. RNA polymerase I
b. RNA polymerase II
c. RNA polymerase III
d. RNA polymerase IV
e. RNA polymerase V
a
35
What kind of DNA is the DNA that encodes rRNA?
a. highly repetitive DNA
b. moderately repetitive DNA
c. unique sequence DNA
d. single copy DNA
e. c and d
b
36
You are looking at an electron micrograph of several transcriptional units for rRNA. How can you tell where the transcription initiation site is ________?
a. It is near the longest nascent transcripts.
b. It is near the middle of the Christmas tree.
c. It is near the shortest nascent transcripts.
d. It is always 40 µm from the center of the Christmas tree.
e. c and d
c
37
What is on the 3' end of every mature tRNA?
a. the triplet CCA
b. the anticodon
c. the cloverleaf loop
d. the codon
e. a and b
a
38
Most of the cellular RNA is in what form?
a. hnRNAs
b. tRNAs
c. mRNAs
d. rRNAs
e. hmRNAs
d
39
The genetic code has 64 codons, while there are only 20 amino acids. Thus, some amino acids are coded for by more than one codon. As a result, the genetic code is said to be ________.
a. regenerate
b. degenerate
c. overlapping
d. nonoverlapping
e. nonspecific
b
40
What is the minimum number of tRNAs that a cell could have?
a. 20
b. 3
c. 64
d. 61
e. 21
a
41
Another name for protein synthesis is _________.
a. transcription
b. transition
c. transsubstantiation
d. translation
e. transition state
d
42
Energy from what molecule is used to enable tRNAs to bind to ribosomes during protein synthesis?
a. GTP
b. AMP
c. GMP
d. ATP
e. ADP
a
43
_______ is expended in the formation of the _______ bond of a protein.
a. No energy, H
b. Energy, peptide
c. No energy, peptide
d. Energy, glycosidic
e. No energy, phosphodiester
b
44
What are the three distinct activities of protein synthesis in the correct order?
a. initiation, elongation, termination
b. termination, initiation, elongation
c. initiation, termination, elongation
d. elongation, initiation, termination
e. elongation, termination, initiation
a
45
How do release factors interact with the stop codon in the A site?
a. The release factor possesses a conserved trinucleotide that pairs with the stop codon.
b. The release factor possesses a conserved tripeptide that interacts directly with the stop codon.
c. The release factor possesses a conserved trisaccharide that pairs with the stop codon.
d. They excise the stop codon terminating protein synthesis.
e. They disassemble the ribosome by using the stop codon as a wedge.
b
46
What is the advantage of synthesizing proteins on a polyribosome?
a. It decreases the rate of protein production.
b. It allows the cell to make longer proteins.
c. It increases the rate of protein synthesis.
d. It allows the cell to make shorter proteins.
e. It increases the rate of transcription.
c
47
The Shine-Dalgarno sequence __________.
a. is a ribosome binding site on an mRNA
b. is located upstream (5’) of the start codon
c. is needed for proper translation in eukaryotes
d. a and b
e. a, b, and c
d
48
What is responsible for covalently linking amino acids to the 3'-end of the tRNA?
a. peptidyltransferase
b. aminoacyl-tRNA synthetase
c. the large subunit of the ribosome
d. amino acid synthase
e. ATP synthase
b
49
The process of translation ends as a result of an interaction between which of the following?
a. A stop codon and a protein
b. A stop codon and a tRNA
c. A stop codon and rRNA
d. A stop anticodon and a stop codon
e. A termination signal in the ribosome
a
50
Which of the following statements about microRNAs in animal cells is correct?
a. MicroRNAs are short single stranded RNAs.
b. MicroRNAs can reduce gene expression by inhibiting translation.
c. MicroRNAs typically bind to the coding region of a mRNA.
d. One microRNA can bind to only one type of mRNA.
e. All microRNAs are expressed in every cell, except germ cells (eggs and sperm).
b
51
Cells from a tremendously weakened embryo are examined and found to have seriously depleted levels of a number of tRNAs. The lack of the tRNAs is observed to be primarily due to:
a. a defect in RNA polymerase I
b. a defect in RNA polymerase II
c. a defect in RNA polymerase III
d. a defect in a reverse transcriptase
e. a defect in DNA polymerase
c
52
The antibiotic tetracycline preferentially inhibits _______ and not _________.
a. transcription in certain prokaryotes; transcription in most eukaryotes
b. tRNAs in certain prokaryotes; tRNAs in most eukaryotes
c. ribosomes in certain prokaryotes; ribosomes in most eukaryotes
d. snRNPs in certain prokaryotes; snRNPs in most eukaryotes
e. protein synthesis in all prokaryotes; protein synthesis in most eukaryotes
c
53
Imagine that you are a researcher and have just sequenced the genome of a worm. You have identified a gene you’re calling “Eggers” that you suspect might be involved in the worm’s ability to make eggs. Which of the following statements best describes how you should conduct your experiment?
a. You will feed young worms fragments of double-stranded DNA encoding Eggers and later examine how many eggs the worms produce.
b. You will inject worm eggs with a transposon that carries the Eggers gene, let the eggs hatch, and then see how many eggs the developed, adult worms produce.
c. You will feed young worms RNA transcribed from the Eggers gene and later examine how many eggs the worms produce.
d. You will feed young worms with double-stranded RNA corresponding to the Eggers gene and later examine the number of eggs the worms produce.
e. You will feed the young worms with antibodies specific to the EGGERS protein, and see how many eggs the worms produce.
d
54
If there was one tRNA for every codon that codes for an amino acid, how many different tRNAs should there be?
a. 20
b. 3
c. 64
d. 61
e. 21
d
55
When a cell’s radius increases, its surface area / volume ratio ___________ , which can ___________ the cell’s ability to supply nutrient to the cell’s interior.
a. increases; improve
b. decreases; improve
c. increases; decrease
d. decreases; decrease
e. remains unchanged; increase
d
56
The third tenet of cell theory, described by Rudolf Virchow, states:
a. Cells can arise only by division from preexisting cells.
b. All organisms are composed of one or more cells.
c. Cells are the structural unit of life.
d. All cells have a genetic blueprint stored in the form of DNA or RNA.
e. All cells are enclosed by a cell membrane.
a
57
The following facts about proteins are true except:
a. The secondary structure of proteins includes alpha (α) helices and beta (β) sheets.
b. The tertiary structure of proteins is affected by a variety of molecular interactions, including hydrogen bonding and hydrophobic interactions of the amino acid side chains.
c. Amino acids with hydrophobic side chains are typically found on the outer surface of a protein found in the cell’s cytoplasm.
d. Tubulin is an example of a protein with a structural role.
e. Some proteins are capable of increasing the rates of metabolic reactions.
c – hydrophilic residues are found tucked inside a protein, away from the cytoplasm
58
Following damage to the DNA by ionizing radiation, the ATM protein phosphorylates Chk2 proteins, which then phosphorylate p53. The p53 protein is a ___________ that induces expression of the p21 gene. The p21 protein that is produced now acts as a(n) _______molecule in the signalling pathway.
a. kinase; effector
b. transcription factor; sensor
c. phosphatise; transducer
d. transcription factor; effector
e. kinase; sensor
d
59
One experiment that confirmed the role of myosin II in cytokinesis used
a. antibodies to inhibit the function of myosin II, which caused the cells to undergo nuclear divisions without cell division.
b. antibodies to inhibit the function of myosin II, resulting in rapidly dividing cells.
c. antibodies to enhance the function of myosin II, resulting in multinucleated cells.
d. a drug that prevented anaphase, thereby preventing cell divisions.
e. an inhibitor of microtubule assembly, thereby preventing mitosis.
a
60
Which of the following statements about lamins are correct?
a. Lamins are proteins that line the inner membrane of the nucleus.
b. A defect in a lamin protein is associated with a condition known as progeria, where the affected individual show signs of premature aging.
c. Lamin proteins help bind the heterochromatin.
d. a and b
e. a, b, and c
e
61
During early prophase of mitosis, the two centrosomes begin to move apart with the help of which of the following molecules?
a. microtubules
b. dyneins
c. kinetochore proteins
d. a and b
e. a, b, and c
d
62
A mutated cell has a defective RCC1 protein. Which of the following will likely happen, now that RCC1 is not working as effectively as it should?
a. Ran-GTP levels in the nucleus would increase
b. Ran-GDP levels in the nucleus would increase
c. Import of proteins into the nucleus would slow down
d. a and c
e. b and c
e
63
What kind of molecule commences the inactivation process of the X chromosome during embryonic development?
a. a protein
b. a hormone
c. a noncoding RNA
d. a protein-coding RNA
e. the molecule has yet to be identified
c - Xist is a non-coding RNA (it is not translated)
64
To what are the AT-rich α-satellite sequences at the end of the DNA loops in the 80 – 100 nm fibers (also known as looped domains) attached?
a. DNA polymerases
b. The centromere
c. The spindle
d. A variety of proteins that are part of an organized nuclear scaffold or matrix
e. Heterochromatin
d
65
An examination of a person’s karyotype reveals they have only one X chromosome, and no Y chromosome. This rare condition is a type of
a. aneuploidy
b. monosomy
c. trisomy
d. a and b
e. a and c
d – monosomy (missing a c’some) is a type of aneuploidy
66
Which of the following statements about telomeres is not correct?
a. Telomeres are located at the ends of chromosomes.
b. Telomeres are composed of long stretches of non-repeated DNA sequences.
c. Telomeres help anchor the chromosomes to the nuclear scaffold.
d. As we age, the telomeres in most of our somatic cells get progressively shorter with each cell division.
e. An enzyme called telomerase restores the length of telomeres in certain cell types.
b – telomeres are made of repeated DNA sequences
67
How can the methylation of histone H3 in the nucleosomes upstream of a gene inhibit the transcription process?
a. H3 methylation increases access of RNA polymerase and transcription factors to the DNA template.
b. Methylated H3 inhibits RNA polymerase.
c. Methylated H3 inhibits transcription factors.
d. Methylation of histone H3 promotes chromatin compaction and decreases access to the DNA template.
e. a and d
d
68
Which of the following statements about intron splicing is correct?
a. Intron splicing occurs through the actions of a spliceosome.
b. SnRNPs (“snurps”) contain snRNAs, which help to align the snRNP into position on the mRNA before the intron is spliced.
c. At least one of the snRNAs within a snRNP is thought to be responsible for cutting the RNA.
d. a and b
e. a, b, and c.
e
69
What features of a mRNA molecule can affect its stability or half-life?
a. the presence or absence of 5’ methyl guanosine cap
b. specific nucleotides within the 3’ UTR
c. specific nucleotide sequences within the exons
d. a and b
e. a, b, and c
d – the 5’ cap promotes stability (therefore, it affects longevity); the 3’UTR has sequences that affect stability too.
70
A mutant cell is found to have seriously depleted levels of the 28S rRNA. The lack of this particular rRNA is primarily due to:
a. a defect in RNA polymerase I
b. a defect in RNA polymerase II
c. a defect in RNA polymerase III
d. a defect in a reverse transcriptase
e. a defect in DNA polymerase
a
71
The hydrolysis of GTP provides energy in which of the following steps of translation?
a. During initiation of translation, when the first tRNA is delivered to the ribosome.
b. During the elongation process, when each tRNA binds to the A-site of the ribosome.
c. During the elongation process, when an elongation factor helps the ribosome move along the RNA molecule.
d. a and b
e. a, b, and c
e
72
How are enhancers thought to stimulate transcription despite the large distance separating them from the core promoter?
a. Enhancers can excise intervening DNA.
b. Enhancers and core promoters can be brought into close proximity because the intervening DNA can form a loop and held there through the interactions of DNA-bound proteins.
c. Enhancers can unravel DNA.
d. Enhancers can search through DNA and bind directly to the associated core promoter.
e. Enhancers bind RNA polymerase very tightly.
b
73
The roles of snoRNPs (“snorps”) include
a. removal of the spacer regions on the 45S rRNA.
b. the methylation of some riboses on the rRNA.
c. the removal of the introns from mRNA.
d. a and b
e. a, b, and c
d
74
What is responsible for covalently linking amino acids to the 3'-end of the cognate tRNA?
a. peptidyltransferase
b. aminoacyl-tRNA synthetase
c. glutamine synthetase
d. RNA polymerase
e. ATP synthase
b
75
Which of the following is/are not correct about siRNAs and/or miRNAs?
a. Both siRNAs and miRNAs are generated through the action of an enzyme called Dicer.
b. Both siRNAs and miRNAs are double-stranded RNAs that must be unwound into single stranded RNA molecules before they can bind to their target mRNA.
c. Both siRNAs and miRNAs help guide endonucleases to mRNAs, resulting in mRNA destruction in animal cells.
d. siRNAs can be used to identify the function of genes by creating loss-of-function mutants.
e. miRNAs are naturally-occurring double-stranded RNAs that can turn off genes in certain tissues.
c – siRNAs induce degradation of the mRNA; miRNAs in animal cells block translation, but do not induce mRNA degradation
76
A steroid hormone is an example of a(n)
a. lipophilic carbohydrate
b. lipophobic carbohydrate
c. lipophilic lipid
d. lipophobic lipid
e. amphipathic protein
c
77
Which cell is the least likely to enter into the G0 phase of the cell cycle?
a. A neuron
b. A mature red blood cell
c. A muscle cell
d. A free-living protozoan
e. None of the above
d – the 3 cell types listed in a, b, and c don’t typically divide once they have matured, so they enter into G0 (a non-dividing stage of the cell cycle)
78
A stock of transgenic flies has been generated in the laboratory that produces offspring with eyes (but not bodies) that glow green when they are exposed to ultraviolet light. Which of the following statement(s) is/are true about this transgenic stock of flies?
a. The gene for green fluorescent protein was fused to a promoter that is probably eye-specific.
b. The green fluorescent gene and some regulatory sequences could have been delivered into flies by embryo microinjection or a gene gun.
c. A transposon could have assisted in the integration of green fluorescent protein gene into the flies’ chromosomes.
d. All of the above
e. None of the above.
d
79
To view a cell’s nuclear pore (with a diameter of 100 nanometers), you would need a(n)
a. light microscope
b. electron microscope
c. light telescope
d. electron telescope
e. none of the above
b
80
Which of the following biological macromolecules do not form polymers?
a. lipids
b. carbohydrates
c. DNA
d. proteins
e. RNA
a
81
In fission yeast, wee1- mutants are smaller than normal cells because:
a. the mutant wee1 protein fails to remove a phosphate from Cdk (cdc2 kinase).
b. the mutant wee1 protein adds a phosphate to Cdk (cdc2 kinase), thereby inactivating Cdk and allowing mitosis to occur too early.
c. the mutant wee1 protein fails to add a phosphate to Cdk (cdc2 kinase), which allows the Cdk to become active and initiate mitosis early.
d. a and b
e. a and c
c
82
The role of the MAD2 protein during the “spindle checkpoint” is to
a. prevent sister chromatids from separating during anaphase if the kinetochore microtubules are improperly attached to the kinetochore
b. inhibit cdc20, which would otherwise activate the anaphase promoting complex (APC)
c. degrade securin
d. a and b
e. a and c
d
83
A nuclear localization signal is:
a. a nuclear import protein that carries other proteins into the nucleus.
b. a chemical signal that induces the nucleus to import proteins.
c. an amino acid sequence on a protein that binds to the nuclear pore complex.
d. an amino acid sequence on a protein that binds to a nuclear import protein.
e. none of the above.
d
84
Which of the follow statements about nucleosomes and/or histones is incorrect?
a. Nucleosomes have 8 histones within their core, and one histone on the outside of this core.
b. Within the nucleosome core, there are 4 different kinds of histone proteins.
c. Histones are negatively charged proteins, and this charge helps them bind DNA.
d. The DNA is wound around a nucleosome 1.8 turns (almost twice).
e. The DNA is bound to the nucleosomes with non-covalent bonds.
c
85
Telomerase is an enzyme that:
a. is active in human germ cells but not most healthy human somatic cells
b. repairs shortened telomeres following chromosome replication
c. is active in protozoan cells
d. a and b
e. a, b, and c
e
86
You remove a small part of the promoter region of a particular gene. Once the altered DNA is put back into cells, the cells are able to transcribe the modified DNA even faster than the unaltered DNA. What part of the promoter did you likely remove?
a. core promoter
b. distal promoter
c. proximal promoter
d. the TATA sequence
e. the CAAT sequence
b – the distal promoter can bind specific transcription factors than can either increase or decrease transcription – depending on the factor
87
Which of the phenomena below is responsible for the ability of one gene to code for more than one polypeptide?
a. transcription
b. alternative splicing
c. transposition
d. hybridization
e. exon shuffling
b
88
What features set rRNAs apart from mRNA transcripts?
a. pseudouridine residues and thymidine residues
b. thymidine residues and methylated nucleotides
c. pseudouridine residues and methylated nucleotides
d. pseudouridines and pseudocytosines
e. methylated nucleotides and pseudocytosines
c
89
What is the significance of the variability of the third nucleotide in a codon?
a. Each tRNA can recognize and bind its own codon.
b. Each tRNA can recognize and bind its own amino acid.
c. The same tRNA can recognize more than one codon.
d. The same tRNA can recognize more than one anticodon.
e. The same anticodon can recognize more than one amino acid.
c
90
Why does it make sense that cells would use RNA interference (RNAi) to recognize long double-stranded RNA (dsRNA) and destroy it?
a. long dsRNAs could mean viruses are present.
b. dsRNAs are produced by the cell's normal genetic activity.
c. dsRNAs adversely affect mitochondria.
d. dsRNAs could cause degradation of nuclear DNA.
e. a and d
a – RNAi likely evolved as an antiviral response – we just use it for another purpose to modify gene expression
91
Centrosome alignments and movements during mitosis are mediated by:
a. dynein proteins working with astral microtubules to pull centrosomes apart
b. kinesin proteins working with polar microtubules to push centrosomes apart
c. dynein proteins that align polar microtubules
d. All of the above are correct
e. Two of the above are correct
d
92
Which of the following is/are required for normal intron splicing to occur?
a. A spliceosome
b. U proteins, with at least one having ribozyme activity
c. Small nucleolar RNAs (snoRNAs) within “snorps”
d. Two of the above
e. Three of the above
d
Note: C is incorrect: snorps facilitate rRNA processing; they are not involved in intron splicing. Small nuclear RNAs within snurps mediate intron splicing.
93
Which of the following is the third tenet of cell theory, proposed by Rudolf Virchow?
a. Cells arise only from division from pre-existing cells.
b. All cells are surrounded by a cell membrane.
c. All organisms are composed of one or more cells.
d. Cells are the structural unit of life.
e. All cells use DNA to store genetic information.
a
94
4. The kinetochore:
a. is the site of attachment of kinetochore microtubules to a chromosome
b. includes a region of the chromosome enriched with α-satellite DNA
c. is the site of attachment of the minus end of a kinetochore microtubule to the chromosome
d. a and b
e. a, b, and c
a or d
Note: Some people have interpreted kinetochore as being only the proteins associated with the centromere (and therefore selected A as correct), while others may have interpreted the kinetochore to include both the proteins and the structural DNA to which the proteins attach as being part of the kinetochore (answer D). As I probably didn’t make it absolutely clear that the kinetochore is actually just the protein structure, I will award everyone who chose A or D a mark. C (and therefore E) is incorrect, as the plus end of the microtubule associates with the kinetochore
95
The stability of an mRNA is dependent on:
a. the length of its polyA tail.
b. having a 5’ cap.
c. particular sequences within the 5’ UTR.
d. a and b
e. a, b, and c
d
| Note: mRNA stability is determined by sequences within the 3’ UTR, not the 5’UTR.
96
Which of the following statements about the ATM-mediated DNA damage checkpoint is NOT correct?
a. The ATM protein detects DNA breaks and initiates a cascade of signals to prevent mitosis.
b. The ATM protein is a kinase that directly phosphorylates p53.
c. The ATM-mediated pathway includes a transcription factor that induces the expression of p21.
d. An end result of the ATM-mediated DNA damage checkpoint is the inhibition of the maturation promoting factor (MPF).
e. A defect in the ATM protein can increase the chances of cancer.
b
| Note: The ATM protein directly phosphorylates Chk2, not p53.
97
A natural process that permits the same gene to produce different mRNAs in two different cells, without altering the DNA sequence through any mutational process, is
a. alternative splicing of transcripts.
b. exon shuffling.
c. gene splicing.
d. gene scrambling.
e. None of the above
a
98
Which statement about cytokinesis is correct?
a. Cytokinesis is otherwise known as mitosis.
b. In plants, cytokinesis involves the formation of a contractile ring of proteins.
c. In animal cells, cytokinesis involves the formation of a cell plate to divide the cell into daughter cells.
d. Adding myosin II-specific antibodies to cultured animal cells can lead to multinucleated cells.
e. Every cell division is always preceded by DNA replication in both somatic and germ cells.
d
99
If a spherical cell increases its diameter, which of the following statements are true about the enlarged cell?
a. The cell’s surface area:volume ratio decreases.
b. The cell’s surface area: volume ratio increases.
c. The rate of nutrient inflow will need to be increased.
d. a and c
e. b and c
d
100
A neuron that will not undergo any additional cell divisions is likely in the ____ stage of the cell cycle.
a. G0
b. G1
c. G2
d. G3
e. M
a
101
A chromosome translocation can result in which of the following changes to a cell’s gene?
a. A gene’s sequence can be interrupted, resulting in a truncated or nonfunctional protein.
b. A gene’s expression can be altered, either quantitatively or temporally.
c. A gene’s sequence can be fused with that of another gene, resulting in a hybrid protein.
d. All of the above.
e. Two of the above.
d
102
Model organisms used in cell biology research ideally have the following properties:
a. short life spans
b. sequenced genomes
c. availability of many mutant strains
d. All of the above are correct
e. Two of the above are correct
d
103
The movement of proteins through the nuclear pore is mediated by the diffusion of which molecule through the pore?
a. RCC1
b. RanGAP
c. Nucleoporin
d. RanGTP
e. ATP
d
104
_______ DNA is typically present in ______copy(ies)/genome, and is often used for DNA fingerprinting.
a. Highly repeated; >100,000
b. Moderately repeated; a few to 10,000
c. Non-repeated DNA; one
d. Highly repeated; >1000
e. Moderately repeated; >100,000
a
105
A virus may not be considered a living organism for which of the following reasons?
a. It lacks any genetic material.
b. It lacks any proteins.
c. It cannot replicate on its own.
d. More than one of the above.
e. None of the above.
c
| Note: All viruses contain both genetic material (either DNA or RNA) and proteins.
106
Which RNA polymerase transcribes the 45S transcript?
a. RNA polymerase I
b. RNA polymerase II
c. RNA polymerase III
d. RNA polymerase IV
e. RNA polymerase V
a
107
When describing DNA structure and organization, a looped domain ________.
a. is a loop of 30 nm fiber DNA tethered to the nuclear matrix.
b. refers specifically to a group of proteins of the nuclear matrix.
c. is a specific protein that holds the DNA in place within the nucleus.
d. is a stretch of heterochromatic DNA containing no coding genes.
e. contains no nucleosomes.
a
108
Which of the following statements about Maturation Promoting Factor (MPF) is NOT correct?
a. MPF is composed of two proteins, a kinase and a cyclin.
b. Activated MPF causes the nuclear membrane to break apart during the early phase of mitosis.
c. MPF is activated by the addition of a phosphate by Wee1.
d. MPF can induce the destruction of itself by activating ubiquitin ligase.
e. MPF levels are low during G1 and S phase of the cell cycle
c
109
Histones within heterochromatin are typically more ________ than histones of euchromatin.
a. phosphorylated
b. formylated
c. acetylated
d. methylated
e. ubiquitinated
d
110
Which statement about the XIST gene is NOT true.
a. XIST encodes an RNA that is not translated.
b. X chromosomes that express XIST will eventually acetylate some of their histone proteins.
c. XIST is transcribed on just one X chromosome.
d. XIST plays a role in the formation of Barr bodies.
e. The XIST gene product helps inactivate an X chromosome.
b
111
Which statement about telomeres and/or telomerase is correct?
a. Telomerase is expressed in most somatic cells in humans.
b. Cancer cells often have restored telomerase expression.
c. Telomerase is absent in protozoans (single-celled organisms).
d. Dolly, the cloned sheep, had longer than normal telomeres.
e. Telomerase is not produced in stem cells.
b
112
Which of the following are possible functions of nucleotides within cells?
a. Nucleotides are components of the cell’s genetic material.
b. Nucleotides can serve as signaling molecules.
c. Nucleotides can serve as energy transfer molecules.
d. Two of the above
e. Three of the above
e
113
A nucleosome is _________.
a. an electron dense region within the nucleus.
b. a group of negatively charged proteins around which the DNA is wound.
c. comprised of a group of eight histone proteins within its core.
d. Two of the above are correct
e. Three of the above are correct
c or d
Note: I will accept either answer C (which assumes you do not regard nucleosomes as constituting a “region” in the nucleus) or answer D, because you can argue that nucleosomes can be visualized with high magnification electron microscopy, and they appear electron dense relative to the surrounding nucleoplasm (not exactly a “region”, but nevertheless an electron dense object.
114
Which of the following statements about protein structure is correct?
a. The secondary structure refers to the protein’s amino acid sequence.
b. Primary structure refers to beta sheets and alpha helices.
c. Tertiary structures can arise from ionic interactions between alpha helices.
d. Tertiary structure refers to the joining of two or more protein subunits together.
e. Quaternary structures are dependent only on hydrophobic interactions between protein subunits.
c
115
Which statement about cellular carbohydrates is NOT correct?
a. Cellulose is a polymer of glucose subunits that is not digestible by animals.
b. Starch is an unbranched glucose polymer of animal cells.
c. Glycogen is a branched glucose polymer.
d. Carbohydrates are commonly used as energy storage molecules within the cell.
e. The subunit of a polymer of carbohydrates is called a monosaccharide.
b
116
A DNA regulatory sequence found 10,000 base pairs upstream of gene’s transcription start site is most likely the gene’s ______.
a. core promoter
b. distal promoter
c. proximal promoter
d. enhancer
e. TATA box
d
117
If an evil scientist wanted to genetically modify a chimpanzee, what type of DNA sequences would he need to alter the most to ensure that gene expression more closely resembled that of a human?
a. Intron sequences
b. Exon sequences
c. Promoter sequences
d. Heterochromatin sequences
e. Telomere sequences
c
Note: To affect gene expression (not just gene sequence), you need to make the greates number of changes in the regulatory sequences – i.e. the promoters of the genes.
118
What is a nuclear localization signal (NLS)?
a. A DNA sequence that allows the DNA to enter the nucleus.
b. A region of a protein that can bind to an importin protein.
c. A region of a protein that binds directly to a nucleoporin protein.
d. Two of the above
e. None of the above
b
Note: The NLS does not attach directly to the nucleoporins. The NLS binds to one subunit of the importin protein; the other subunit of the importin binds to the nucleoporin.
119
Which statement about microRNAs (miRNAs) is correct?
a. MiRNAs are short single-stranded RNAs.
b. In animal cells, miRNAs typically bind to exon sequences.
c. In animal cells, miRNAs prevent translation of targeted transcripts.
d. One miRNA can silence only one gene.
e. More than one of the above is correct
c
Note: A is incorrect – miRNAs are double-stranded; B is incorrect – in animal cells, miRNAs bind to the 3’ UTRs, not exons; D is incorrect – one miRNA can silence many different genes.
120
Progeria is a condition characterized by:
a. premature aging
b. a defect in a nuclear lamin protein
c. irregularly-shaped nuclei
d. a and b
e. a, b, and c
e
121
The first steps of ribosome attachment to mRNAs in eukaryotes involves _______.
a. The ribosome finding a Shine-Delgarno sequence.
b. the large subunit of the ribosome binding first to the mRNA.
c. elongation factors binding the small ribosome subunit and then the mRNA
d. the small ribosome subunit binding eukaryotic initiation factors (eIFs) and then binding the mRNA.
e. both ribosome subunits binding the mRNA simultaneously.
d
122
The movement of which type of molecules in or out of the nucleus is typically closely regulated by nuclear pores?
a. Water
b. Monosaccharides
c. Proteins
d. Monomeric nucleotides such as ATP
e. Ions
c
123
Transcription coactivators are proteins that __________.
a. regulate the transcription of genes
b. bind directly to DNA regulatory sequences
c. alter histone-DNA interactions
d. All of the above are correct
e. Two of the above are correct
e
Note: A and C are correct statements, but B is incorrect – transcription coactivators do not bind directly to the DNA (this was an added note to lecture 9, slide 19)
124
In RNA interference, gene silencing is achieved by adding _______ into a cell, which is then chopped up into short interfering RNAs (siRNAs) by ______.
a. double-stranded RNA; an exonuclease
b. single-stranded RNA; Dicer
c. double-stranded RNA; Dicer
d. double-stranded RNA; an exonuclease
e. antisense RNA; Slicer
c
Note: While A and D are the same answer, they are incorrect; Dicer chops up the dsRNA (and it is an endonuclease, not an exonuclease).
125
Which of the following enzymes are often used to repress transcription of a gene?
a. Histone methyltransferases
b. DNA methyltransferases
c. Histone acetyltransferases
d. a and b
e. a, b, and c
d
| Note: Histone acetyltransferases activate gene expression, not repress it.
