Biochem exam review
38. A constitutive high- level expressio of c-fos or c-jun in cells will lead to: a. no real consequence b. cell death c. activation of cdk4/6 activity in the absence of growth factors d. cell cycle arrest
C
12. Mitogens are added to the medium of cultured human cells that are synchronized in mitosis. The mitogen is washed way after these cells have passed the restriction point in the cell cycle. These cells will progress through the cell cycle then arrest in which phase? A. S phase B. G0-G1 phase C. G2 phase D. Mitosis phase E. all phases
B
14. How did Meselson and Stahl distinguish between semiconservative and conservative replication in their experiment? a) After two rounds of replication, only mixed DNA molecules were present in the gradient. b) After one round of replication, only mixed DNA molecules were present in the gradient. c) After one round of replication, only heavy DNA molecules were present in the gradient. d) After one round of replication, only mixed DNA strands were present in alkaline gradients. e) After two rounds of replication, only heavy DNA strands were present in alkaline gradients
B
32. Which cyclin increases during G2 to prepare for mitosis? 1. A 2. B 3. C 4. D 5. E
2. B.
2. Suppose that the DNA from a particular bacteria has a base composition of 27% T. According to Chargaff's rules, and the structure of ds DNA, what will be the percentage of G?
23%
10. Acetylation of Lysine on the tail of Histone H4 promotes a _____ state of chromatin. a) Open and less condensed b) Closed and condensed
A
10. The nucleosome unit of chromosomal DNA: a. Involves about 200 bp of DNA in each nucleosome repeating unit b. Has a core protein body composed exclusively of histone H1 c. Is found only at chromosome ends d. Does not depend on proteins for its structure
A
11. Higher chromosome compaction and structure depends on: a. SMC proteins, that are a major components of the chromosome scaffold. b. the formation of a chromosome scaffold by topoisomerases. c. the presence of the H1 protein, which promotes formation of the nucleoid. d. the formation of a chromosome scaffold by histone acetylases.
A
11. RNA polymerases are able to correct errors in transcripts via: A. Pyrophosphorolysis, which is known as "kinetic proofreading" that relies on the slowing down of polymerase after incorrect rNTP insertion. B. Sigma factors that recognize specific rNTP mis-insertions and correct them. C. Nucleolytic proofreading, which disengages the polymerase from the template so that it can restart transcription from the promoter. D. Elongation factors that recognize error during elongation and recruit special auxiliary factors that correct the error
A
13. At each replication origin, DNA replication proceeds in a) Both directions from the origin b) Only in one direction from the origin c) Both directions in prokaryotes but one direction in eukaryotes d) Both directions in eukaryotes but one direction in prokaryotes
A
15. The role of retinoblastoma protein (Rb) in regulation of the cell cycle is best characterized as A. Inhibits transcription of critical genes by complexing with E2F transcription factors B. Activates transcription of critical genes by complexing with E2F transcription factors C. Activates cyclin dependent kinases D. Inhibits cyclin dependent kinases E. Promotes cyclin degradation
A
17. The following Cyclin Cdk complex phosphorylates the ORC complex and triggers DNA unwinding, replication inititation while at the same time preventing re- replication A. Cyclin A-Cdk2 B. Cyclin B - CdK4/6 C. Cyclin D-Cdk4/6 D. Cyclin B-Cdk1
A
17. The following exonuclease activity is essential for proofreading function of DNA polymerase a) 3' to 5' b) 5' to 3' c) 2' to 5'
A
19. During removal of RNA primers from eukaryotes a) both b and c choices are true b) RNase H1 removes all RNA primer except for one last ribonucleotide c) FEN1/RTH1 removes the last ribonucleotide left behind by RNSAeH1 d) DNA polymerase 1 removes all of the primer.
A
20. The following exonuclease activity is essential for proofreading function of DNA polymerase a. 3' to 5' b. 5' to 3' c. 2' to 5'
A
21. Failure of which cell cycle checkpoint is most likely to result in aneuploidy and chromosome loss? A. Spindle checkpoint B. DNA-damage checkpoint C. unreplicated DNA checkpoint D. a and b
A
21. In the absence of telomerase, the chromosome ends would ____________ with every round of DNA replication. a. shorten b. lengthen
A
27. The following proteins are involved in mismatch repair a. MutS, MutH, MutL b. Ku70, Ku80, c. UvrA, UvrB, UvrC d. XP-C, XP-G, XP-H
A
3. Short stretches of quadruplex DNA structures exist in the following regions of human genome. a) both b and d choices below are true b) G rich c) homologous d) chromosomal end regions called telomeres e) A rich
A
34. The role of retinoblastoma protein (Rb) in regulation of the cell cycle is best characterized as: a. Inhibits transcription of critical genes by complexing with E2F transcription factors b. Activates transcription of critical genes by complexing with E2F transcription factors c. Activates cyclin dependent kinases d. Inhibits cyclin dependent kinases e. Promotes cyclin degradation
A
40. The following are the negative regulators of the cell cycle and specifically inhibit Cdk4 and Cdk6 activity a. INK4 class of proteins b. Rb class of proteins c. E2F and p53 d. CIP class of proteins
A
42. We discussed an experimnt in class that compared the cell cycle profile of cells with wild type p53 and p53 null ( knockout ) cells at 8 hours after irradiation with gamma rays. In this experiment the cells were sorter based on their DNA content : a. True b. False
A
50. Which of the following is not true of the coding strand of DNA? a. Its sequence is the complement of the primary transcript. b. Its sequence is the complement of the template strand. c. It may be located in either strand of a given chromosome. d. It is also known as the nontemplate strand. e. Its sequence is the complement of the strand of DNA copied during transcription
A
51. Which of the following is true of RNA synthesis (transcription)? a. RNA synthesis is always in the 5' - 3' direction. b. RNA polymerase needs a primer to initiate transcription. c. In transcription, U is inserted opposite T. d. New nucleotides are added on to the 2' OH of the ribose sugar
A
6. Which of the following is not true of the interaction of TBP with DNA? A. TBP binds the TATA box through major groove DNA contacts. B. TBP binds the TATA box through minor groove DNA contacts. C. TBP binding to DNA has a saddle like appearance. D. The DNA bound by TBP is bent.
A
7. Heating causes the 2 strands of DNA to unwind - called 'melting'. When this happens a. The absorbance of DNA at 260nM increases and this effect is called the Hyperchromic effect b. The absorbance of DNA at 260nM decreases and this effect is called thr Hyperchromic effect c. The absorbance of DNA at 260nM is unchanged and this effect is called the Hyperchromic effect d. DNA cannot be unwound or seperated or melted
A
9. Acetylation of Lysine 16 on the tail of Histone H4 promotes a _____ state of chromatin a. Open and less condensed b. Closed and condensed
A
One reason Why dNTPs are used as precursors for the DNA polymerase reaction rather than dNDPs is.. a. The drawback to using dNDPs is that the reverse reaction is easily initiated by Pi, which is a common molecule in the cell. Using dNTPs produces PPi, which is rapidly eliminated thereby making the reaction thermodynamically favorable b. There is significantly higher amount of dNTP available in the cell c. Only dNTP's are recognized by DNA polymerase d. dNDP's are chemically more unstable than dNTP's e. a and d choices are correct
A
The function of DNA ligase is to: A. catalyze the formation of covalent bonds between adjacent nucleotides. B. unwind the double-stranded DNA prior to replication. C. keep the single strands of DNA apart during replication. D. facilitate DNA repair
A
14. If protein synthesis inhibitors are added along with growth factors to quiescent cells A. both early response and delayed response gene transcription is induced B. only early response genes are induced and delayed genes are blocked C. early response gene transcription is blocked and delayed response gene transcription is induced D. both early response and delayed response gene transcription is blocked
B
15. Polymerase switching occurs only on the leading strand during eukaryotic replication. a. True b. False
B
16. Replicated circular DNA molecules are separated by _____ a) Type I topoisomerases b) Type II topoisomerases c) DNA polymerase d) Primase
B
19. Replicated circular DNA molecules are separated by _____ a. Type I topoisomerases b. Type II topoisomerases c. DNA polymerase d. Primase
B
19. Which of the following is a target of the APC? A. P53 B. Cyclin B C. separase D. a and b
B
2. DNA is a double helical molecule with the polarity of the two strands being a. Parallel b. Antiparallel c. Homologous d. Identical
B
20. The RNA component of telomerase is important because: a) It codes for the protein component of telomerase. b) It is the template used for directing the synthesis of the telomere units. c) It is a structural component that holds the telomerase subunits together. d) It binds telomerase to the nuclear membrane.
B
22. The RNA component of telomerase is important because: a. It codes for the protein component of telomerase. b. It is the template used for directing the synthesis of the telomere units. c. It is a structural component that holds the telomerase subunits together. d. It binds telomerase to the nuclear membrane.
B
23. Suppose the stretch of DNA shown below underwent a mutational change as indicated by underlining. With no knowledge of the functional role of this stretch of DNA, which answer gives the best characterization of this mutational change? AGCTCTGA ------> AGCTCCGA TCGAGACT ------> TCGAGGCT a. A transversion b. A transition c. A translocation d. A frame shift e. An insertion
B
23. Which of the following inhibits cyclin A/Cdk2 activity A. INK4 B. p21CIP C. Rb D. a and c
B
26. Deamination of cytosine bases is a common occurrence in DNA. Such errors are corrected beginning with the use of which protein/enzyme? a. Endonuclease b. DNA glycosylase c. Proofreading by DNA polymerase d. 5' Exonuclease e. Ku70/80 dimer
B
28. Which of the following is the result of external mutagens? a. DNA polymerase replication errors b. addition of bulky adducts to the DNA c. depurination d. recombination errors
B
29. The following kinases are activated by DNA damage; a. cdk4-cyclinD and cdk1-cyclinB b. ATM and Chk2 c. DNA PK and Ku70 d. ATM and cdk1-cyclinB
B
3. Which statement concerning Form B DNA is FALSE? a. Approximately 10 base pairs generate one complete turn of the helix. b. A and T rich regions of double stranded DNA are the most stable to denaturation. c. The two individual polynucleotide chains runs with opposite polarities to one another. d. The molar content of purine bases equals the molar content of pyrmidine bases.
B
4. Which is NOT a correct statement regarding the base pairing rules for B-form DNA? a. A purine always pairs with a pyrimidine b. Guanine pairs with Cytosine via 1 hydrogen bond c. Adenine pairs with Thymine via 2 hydrogen bonds d. In RNA, adenine pairs with uracil instead of thymine
B
43. In the same experiment mentioned above, it was observed that p53 null cells a. showed a better arrest in G1 phase after irradiation as compared to wild type cells b. did not show a G1 arrest wheras wild type cels did arrest in G1 pase c. did notshow G1 and G2 arrest d. showed S phase arrest
B
45. Which statement concerning a promoter in E. coli is CORRECT? a. All promoters are recognized by a single sigma factor. b. Critical DNA sequences are found about -10 and -35 bp from the transcriptional start point. c. Sigma factor remains bound to promoters at all times. d. RNA polymerase holoenzyme binds to transcription factors and not directly to DNA.
B
47. Which of the following regarding 5s rRNA is not true? a. It is transcribed by RNA polymerase III b. It is transcribed by RNA polymerase I c. It is a components of the large subunit of the ribosome d. It has internal promoter sequences
B
49. In the context of mRNA synthesis in mammalian cells, the "zinc finger domain" is associated with: a. The way in which TAFs associate with TATA box binding protein b. The most common protein domain used by transcription factors for recognition of DNA sequences. c. The active site of RNA polymerase II d. The "transactivation" region of a sequence-specific transcription factor e. Proof reading by RNA polymerase
B
7. The nucleosome consists of an octameric histone core that contains a) 2 molecules each of H1, H2, H3, and H4. b) 2 molecules each of H2A, H2B, H3, and H4. c) 2 molecules each of H2, H3, H4, and H5. d) 1 molecule each of H1 and H2A and 2 molecules each of H2B, H3, and H4.
B
8. What is the function of TFIIH in the transcription initiation complex? A. binding to the TATA box B. unwinding the DNA duplex C. catalyzing the synthesis of RNA D. all of the above
B
9. All of the following are true about histone chemical modification EXCEPT. a) Modification almost always happens in the histone tails. b) Modifications are irreversible. c) Modifications can be inherited.
B
Each replication fork requires both leading and lagging strand synthesis because A. DNA polymerases can only synthesize DNA 3' to 5'. B. the DNA templates are antiparallel and yet the DNA polymerases only work in one direction. C. the helicase unwinds one strand faster than the other. D. All of these choices are correct.
B
1. The sequence of the messenger RNA molecule (primary transcript) synthesized from a DNA molecule with a coding strand having the sequence 5' ATGCTACCGTTA is: A. 5' UACGAUGGCAAU. B. 5' UAACGGUAGCAU. C. 5' AUGCUACCGUUA. D. 5' AUUGCCAUCGUA. E. None of the choices given is correct.
C
11. Observing replication of circular plasmid DNAs (prokaryotic DNA) by electron microscopy showed that: a) replication initiates at multiple origins, creating multiple replication bubbles in the plasmid. b) template strands completely unwind before replication starts. c) replication initiates from a single origin, creating a single replication bubble in the plasmid. d) the plasmid DNA must become linear before replication can initiate at each end of the linear plasmid.
C
12. DNA replication is said to be "semi conservative." This term refers to which aspect of replication? a) Retention of one phosphate from the nucleotide triphosphates that are polymerized. b) Type of hydrogen bonding that occurs c) Overall process by which each individual strand of the ds DNA helix is passed to the cells of the next generation d) Orientation of each individual strand of the helix with respect to the other
C
12. Which of the following is not true about histone modification and the enzymes that create them? a. The enzymes responsible are often part of multiprotein complexes that include transcription factors. b. The modifications can be passed on by epigenetic inheritance. c. The enzymes responsible for the modifications can create histone variants. d. All of these choices are correct.
C
13. A constitutive, high expression of the early response genes c-jun and fos will lead to: A. No consequences B. Cell death C. Activation of Cdk4/cdk6 even in the absence of growth factors D. Cell cycle arrest
C
14. What is responsible for the high processivity of the Pol III holoenzyme? a. Because it has three polymerase cores, it can replicate three times as much DNA. b. The hand-shaped structure of the polymerase core grasps the template DNA. c. The β sliding clamp allows Pol III to stay associated with the DNA template as each nucleotide is added. d. The "thumb" structure of the Pol III polymerase core holds the DNA template tightly.
C
16. The enzyme that synthesizes RNA primer in eukaryotes is a. DNA polymerase d b. DNA polymerase a c. Primase d. RNA polymerase II
C
16. The role of p53 in regulation of the cell cycle can be characterized as: A. Inhibits transcription of critical genes by complexing with E2F transcription factors B. Activates transcription of critical genes by complexing with E2F transcription factors C. Stimulates transcription of genes for cyclin inhibitory proteins D. Inhibits transcription of genes for cyclin inhibitory proteins E. Stabilizes cyclins to diminish their degradation
C
17. Each replication fork requires both leading and lagging strand synthesis because a. DNA synthesis must be complementary. b. DNA polymerases can only synthesize DNA 3' to 5'. c. the DNA templates are antiparallel and yet the DNA polymerases only work in one direction. d. the helicase unwinds one strand faster than the other. e. All of these choices are correct
C
18. A function of PCNA during eukaryotic DNA replication is: a) to polymerize the dNTP's b) to unwind the DNA c) to make DNA polymerase epsilon processive d) both b and c are choices
C
18. APC or Anaphase promoting complex has the following enzymatic activity A. Kinase activity B. Polymerase activity C. E3 ubiquitin ligase activity D. Transcriptional activity
C
2. Which of the following statements regarding transcription only apply to eukaryotes and not to prokaryotes? A. A single RNA polymerase transcribes genes that encode mRNAs, tRNAs, and rRNA. B. Sigma (σ) subunit detaches from RNA polymerase shortly after transcription has initiated. C. The C-terminal domain of the polymerase is phosphorylated after transcription has initiated. D. RNA synthesis is inhibited by actinomycin D.
C
22. Exit from mitosis depends upon the degradation of A. cyclin D B. condensin. C. cyclin B. D. APC
C
25. Xeroderma Pigmentosum is a genetic disease characterized by a. Loss of melanin pigment in the skin. b. Hypersensitivity to infrared radiation. c. A defect in Nucleotide excision repair. d. A defect in Homologous recombination . e. A Cyclin B defect
C
3. Which of the following is not true of the reaction catalyzed by RNA polymerases? A. The 3'-hydroxyl group of the growing RNA strand is a nucleophile. B. The reaction is magnesium ion-dependent. C. U residues are incorporated into the RNA to pair with T residues of the template. D. The RNA molecule is synthesized in the 5' to 3' direction.
C
31. The period of DNA synthesis in continually dividing mammalian cells occurs: a. Just after mitosis b. Just before mitosis c. Is separated from the preceeding and the following mitosis by Gap periods d. Continuously dividing cells do not replicate their DNA
C
36. The "restriction" or "commitment" point of the cell cycle refers to the point at which: a. Daughter chromosomes finally separate from each other at mitosis b. Metaphase chromosomes are most condensed c. Further growth factor stimulation is no longer required to promote cell cycle progression d. Hemi-methylated sites on newly replicated DNA become fully methylated e. The cell first becomes sensitive to growth factor stimulation following the last mitosis
C
39. If protein synthesis inhibitors are added along with growth factors/mitogens to queiscent cells the early response genes are induced because a. no proteins are required for trascriptional induction of early response genes b. no phosporylation is required for transcritpioanl induction of early response genes c. no new protein synthesis is required for transcriptional induction of early response genes d. early response genes do not require growth factors
C
4. Which of the following molecules inhibits bacterial transcription by prevention of promoter clearance? A. -amanitin B. actinomycin D C. rifampicin D. acridine
C
48. Which feature of transcription is NOT a feature of DNA replication? a. Phosphodiester linkages are formed. b. It proceeds in the 5' --> 3' direction. c. It is primer-independent. d. It requires a DNA template. e. It depends on Watson-Crick base pairing.
C
5. Which of the following bases is not found in RNA? a. adenine b. guanine c. thymine d. cytosine e. uracil
C
6. The A form of nucleic acids is a right handed helix formed by a. Only RYRYRY sequences b. Only purines c. RNA- RNA double helix d. Only Pyrimidines
C
7. Which of the following models for RNA polymerase II transcription termination is analogous to ρ-dependent termination in bacteria? A. the antiterminator model B. the submarine model C. the torpedo model D. the allosteric model
C
8. Chromatin remodeling complexes such as Swi/Snf a) Serve as signals for DNA damage b) Function exclusively to generate the highly compact chromosomes found at metaphase of mitosis c) Enable nucleosomes to move about to permit opening up of the local chromatin structure. d) Function during DNA replication
C
8. Why is DNA resistant to hydrolysis under alkaline conditions? a. DNA lacks the 3' hydroxyl on the pentose ring, which would have participated in the hydrolysis. b. Deoxyribose forms furanose rings without oxygen, which makes the ring more stable. c. The 2' hydroxyl of the sugar is directly involved in the hydrolysis reaction, and DNA lacks this group. d. The carbonyl of uracil is directly involved in the hydrolysis reaction and DNA lacks this base. e. None of these choices is correct.
C
9. What is the function of the sigma (σ) subunit of E. coli RNA polymerase in transcription? A. It contains the polymerase active site. B. It contains the separate exonuclease site required for proofreading. C. It directs the polymerase to bind a specific type of promoter sequence. D. It signals the polymerase to terminate transcription at specific sites. E. It allows template-independent RNA synthesis.
C
What are the major differences between helicases, topoisomerases, and ligases used in DNA replication? a) Helicases and topoisomerases unwind DNA: topoisomerases in the pre-replication process, while helicases relieve supercoil stress ahead of the replication process—and ligases seal DNA that has been broken or synthesized as Okazaki fragments. b) All three unwind DNA, but helicases do so before the replication machinery, ligases with the machinery, and topoisomerases ahead of it. c) Helicases and topoisomerases unwind DNA: helicases in the pre-replication process, while topoisomerases relieve supercoil stress ahead of the replication fork—and ligases seal DNA that has been broken or synthesized as Okazaki fragments. d) Helicases and topoisomerases bind double-stranded DNA, and ligases bind RNA-DNA hybrids.
C
1. If you order two synthetic strands of DNA that will then be combined as a Watson Crick helix, you must write each strand 5' to 3'. What is the correct Watson-Crick complement to pair with 5'-GTCA-3'? a. 5'-CAGT-3' b. 5'-GTCA-3' c. 5'-ACTG-3' d. 5'-TGAC-3'
D
1. In the Hershey and Chase experiment that demonstrated that DNA is the genetic material a) The radioactive isotope 32P was recovered in the isolated progeny phage particles b) The radioactive isotope 35S was not recovered in the isolated progeny phage particles c) A kitchen blender was used to separate the empty phage particles after the genetic material was injected in bacteria d) All of the above
D
10. The processes carried out by RNA polymerases and DNA polymerases are in some ways very similar, but they also have striking differences, including which of the following? A. RNA polymerases do not require a primer to initiate synthesis. B. DNA polymerases use both strands of DNA as templates. C. RNA polymerases use only defined stretches of the DNA as templates. D. All of the above. E. Only a and c are correct
D
18. What is the purpose of single stranded DNA binding (SSB) proteins during replication? a. to "unzip" the DNA and separate parental strands b. to relieve "overwinding" of DNA c. to proofread newly synthesized DNA d. to prevent reformation of base pairs
D
20. Arrest of the cell cycle following damage to DNA is initiated by which factor? A. P53 B. Cyclin dependent kinase C. Caspase 3 D. ATM (ataxia telangiectasia mutated) protein E. Cyclin E
D
24. The following shows the first 12 nucleotides of an mRNA as well as a mutated variant. What is the term that describes this type of mutation? 5'-AUGGUUUCACUA-3' Normal /wild type 5'-AUGGUUUAACUA-3' Mutant A. Silent mutation. B. Frameshift mutation. C. Transition. D. Transversion.
D
24. The nonhomologous end joining pathway (NHEJ) for double strand break repair is characterized by: a. Generation of single strand regions that search for base-pairing on a sister chromatid. b. Initiation by DNA glycosylases that cleave the base-sugar linkage c. Production of "crossover" events between identical chromosome regions d. Capping of double strand ends by the Ku70/80 protein complex e. Use of telomerase to create new functional chromosome ends
D
25. Doxorubicin is used to treat many cancers because: A. It reduces the processivity of RNA polymerase B. Prevents sigma factor from binding DNA C. It intercalates between DNA and causes single strand mutations D. It intercalates between DNA and causes double strand breaks
D
30. Cisplatin is a mutagen that causes chemical reactions that the cell cannot easily repair; nevertheless, cisplatin is used to fight many cancers. The logic is that a. cisplatin is an alkylating agent and therefore only mutates oncogenes. b. cisplatin causes cross-linking of purines and purines are more often found in genes important in cell growth and division. c. cisplatin is a photolyase mimic and removes purine cross-links, including the ones it induces. d. cisplatin is an alkylating agent forming covalent adducts and thus blocks replication forks which are more common in dividing cells, such as cancer cells.
D
33. Cyclins function as: a. Protein kinases b. Transcription factors c. Protein phosphatases d. Regulatory modulators of protein kinases called CDK's
D
35. A mutation in p53 will likely lead to cancer because a. Cell will grow healthier and faster b. Cell become immortalized and thus undergo senescence c. Cells will undergo necrotic cell death d. Cell will not repair DNA damage effectively due to lack of cell cycle arrest when needed
D
41. Caspases play what role(s) in the cell? a. They form channels in the outer mitochondrial membrane to release cyt C b. They promote calcium release from the endoplasmic reticulum c. They are cell surface receptors that are stimulated by activated T lymphocytes d. They are proteases that cleave next to aspartic acid to trigger apoptosis
D
44. Which of the following statements about eukaryotic RNA's and RNA polymerases is/are true? a. RNA polymerase III is located primarily in the nucleolus. b. Pre-mRNA/heterogenous nuclear RNA (hnRNA) production involves RNA polymerase II. c. RNA polymerase III produces tRNAs d. b and c are correct e. only a is correct
D
46. In mammalian cells, "enhancer" regions that affect gene expression: a. are binding sites for TATA box binding protein (TBP) b. define the actual start site of a messenger RNA c. are termination sites for transcription d. may lie hundreds of bp away from the promoter
D
5. "DNA footprinting" is a technique that can be used to identify: A. a region of DNA that has been damaged by mutation. B. the position of a particular gene of a chromosome. C. the position of internally double-stranded regions in a single-stranded DNA molecule. D. the specific binding site of polymerase, or other protein on the DNA. E. All of the choices given can be identified by this technique.
D
6. Which of the following statements about supercoiling of DNA are true? (1) Supercoiled DNA differs in linking number from relaxed DNA. (2) Supercoiled DNA can be relaxed through the action of topoisomerases. (3) All DNA in the cell is positively supercoiled. (4) Supercoiled DNA is difficult to unwind. a) Only 2, 3 and 4 are true" b) Only 1, 2 and 3 are true" c) Only 1 and 3 are true d) Only 1 and 2 are true
D
14. The two DNA polymerases that are involved in E coli DNA replication are
DNA polymerase I and III
37. APC is a ubiquitin ligase that causes the degradation of: a. CyclinB Cdk1 b. Proteins that keep sister chromatids together ( Securin / separase)/Anaphase inhibitor c. APC is a transcription factor that controls synthesis of Cyclin B and cyclin A d. APC targets p53 and Rb for degradation. e. choices a and b are correct
E
5. The A form of nucleic acid is a right handed helix formed by
RNA-RNA hybrids
4. DNA is a double helical molecule with the polarity of the two strands being
antiparallel
15. The function of SSB is to
b) Bind to the single stranded DNA templates and keep them from base-pairing