Biochemistry Exam 3
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- 1.The component(s) of DNA which is responsible for the absorbance band at 250-270 nm is
- A.
Bases, pentoses, and phosphates all contribute
- B.
Only bases
- C.
Only bases and pentoses
- D.
Only pentoses and phosphates
- 2.The oligonucleotide, AUGGp, has all these properties except
- A.
Composed of ribonucleotides
- B.
Contains a 3' phosphate
- C.
Composed of deoxyribonucleotides
- D.
Contains three phosphodiester bonds
- 3.An individual heterogeneous nuclear RNA (hnRNA)
- A.
Contains intron sequences not found in the final mature mRNA.
- B.
Contains exon sequences which are removed prior to translation.
- C.
Encodes more than one protein.
- D.
Can be found in the cytoplasm.
- 4.The RNA molecules which are involved in processing the hnRNA are
- A.
MRNA
- B.
TRNA
- C.
RRNA
- D.
SnRNA
- 5.What statement is incorrect about the different RNA molecules?
- A.
TRNAs contain numerous intramolecular hydrogen bonds between bases.
- B.
There are more distinct tRNA molecules than there are rRNA molecules.
- C.
RRNAs are complexed to proteins in the ribosome.
- D.
The most abundant RNA molecule in the cell is mRNA.
- 6.Which of the following is not a characteristic for DNA synthesis?
- A.
DNA polymerase adds nucleotides in a 5'--> 3' direction
- B.
A primer strand of DNA must contain a free 3'-OH end
- C.
The primer strand of DNA determines which nucleotides are added next
- D.
The correct complementary hydrogen bonding between base pairs is the primary check on the fidelity of the newly synthesized DNA
- 7.A DNA is found to exhibit a melting temperature of 75 C in 0.1 M NaCl. Under what experimental conditions would the Tm be increased?
- A.
Decreasing the concentration of DNA.
- B.
Increasing the concentration of NaCl in the solution.
- C.
Adding 1% urea (an organic denaturant).
- D.
All of the above.
- 8.A feature which is distinctive to Z-DNA is
- A.
A left-handed helix
- B.
It has 12 bases per turn
- C.
It is found in vivo
- D.
All of the above
- 9.The linking number of a highly supercoiled plasmid can be readily changed without producing a relaxed DNA by
- A.
Changing the temperature
- B.
Increasing salt concentration
- C.
The action of topoisomerase
- D.
The action of a nuclease such as pancreatic DNase
- 10.Which of the following double-stranded DNAs may convert to a cruciform structure?
- A.
ATGCATGCATGCATGC / TACGTACGTACGTACG
- B.
CATTAAGCAGTGCTTAAGA / GTAATTCGTCACGAATTCT
- C.
ATATATATGCGCGCGCGC / TATATATACGCGCGCGCG
- D.
AAAAAAAAACCCCCCCCC / TTTTTTTTTGGGGGGGG
- 11.Which statement is incorrect about the structure of native E. coli chromosomal DNA?
- A.
The DNA is primarily in the B-helix.
- B.
The DNA is circular and supercoiled
- C.
The DNA exists as a right-handed double helix.
- D.
The DNA is one large linear piece about 4000 kb in length.
- 12.E. coli DNA polymerase I has all the following characteristics except
- A.
A 5'-3' exonuclease activity on a second subunit in the polymerase
- B.
A 3'-5' exonuclease activity
- C.
A 5'-3' DNA polymerase activity
- D.
Modest processivity (ca. 20 nucleotides)
- 13.In the repair of DNA, the E. coli DNA polymerase involved performs which function in addition to its polymerase activity?
- A.
It recognizes the abnormality in the duplex DNA structure.
- B.
It nicks the DNA to provide a 3'-OH.
- C.
It removes the damaged section of DNA with its 5'-3' exonuclease activity.
- D.
It ligates the DNA after the repair synthesis.
- 14.The Klenow fragment of E. coli DNA polymerase I can be used to add nucleotides to a DNA with staggered ends if the ends
- A.
Are recessed with 5'-phosphates
- B.
Are recessed with 3'-OHs
- C.
Are extended with 5'-phosphates
- D.
Are extended with 3'-OHs
- 15.Which of the following is not a characteristic of replication of the E. coli circular chromosome?
- A.
Replication is bidirectional.
- B.
It initiates at a unique position called oriC.
- C.
Torsional stress introduced in the duplex DNA is relieved by DNA gyrase.
- D.
The unwinding of the duplex DNA is driven by the translocation of the DNA polymerase.
- 16.E. coli replication on the lagging strand
- A.
Is primarily carried out by DNA polymerase I
- B.
Is synthesized continuously
- C.
This DNA strand is synthesized in a 3'-5'direction of synthesis
- D.
Is initially synthesized as Okazaki fragments
- 17.Which one of the following characteristics is not associated with E. coli primase?
- A.
It synthesizes the RNA primer in DNA replication.
- B.
It is a specific RNA polymerase.
- C.
It is essential for DNA replication.
- D.
It is also a gyrase
- 18.The polymerase which plays a similar role as that of Prokaryotic polII in eukaryotic replication is?
- A.
DNA polymerase alpha
- B.
DNA polymerase delta
- C.
DNA polymerase gamma
- D.
DNA polymerase kappa
- 19.Which is not a property of E. coli DNA polymerase III?
- A.
It is responsible for incorporating most of the nucleotides in the lagging strand.
- B.
It synthesizes most of the leading strand prior to aiding in the synthesis of the lagging strand.
- C.
It contains a 3¨ to 5¨ exonuclease activity.
- D.
It synthesizes the leading strand and the lagging strand at the same time
- 20.Which statement is incorrect about E. coli DNA polymerase I?
- A.
The cell contains more molecules of DNA pol I than DNA pol III.
- B.
DNA pol I is a single polypeptide with three domains.
- C.
DNA pol I is involved in the repair of UV damaged DNA.
- D.
DNA pol I has a larger turnover number than DNA pol III.
- 21.Which E. coli enzyme has the greatest frequency of incorporating the incorrect nucleotide into its nucleic acid polymer?
- A.
RNA polymerase
- B.
DNA polymerase I
- C.
DNA polymerase III
- D.
Klenow fragment from DNA polymerase I
- 22.DNA-dependent RNA polymerase acts on the DNA template in eukaryotic cells in the synthesis of
- A.
A 5'-3' hnRNA transcript as the RNA polymerase moves in the 3'-5' direction on the DNA template
- B.
A mature RNA transcript as the RNA polymerase moves in the 5'-3' direction
- C.
An RNA transcript, with the sigma subunit of polymerase dissociating after the initiation event
- D.
An RNA transcript, which is complementary to the sense strand of the DNA, except for the replacement of uridines for the thymidines
- 23.The shorter the primer, the more specific the DNA.
- A.
True
- B.
False
- 24.Z-DNA can be stable in A:T-rich regions allowing its transition from B-DNA form.
- A.
True
- B.
False
- 25.Due to nitrogenous bases, UV abs. of DNA increases when heated above body temperature.
- A.
True
- B.
False
- 26.The rate of DNA renaturation is an index of its homology.
- A.
True
- B.
False
- 27.Stacked base pairs absorb less light in native DNA.
- A.
True
- B.
False
- 28.________studies the way genes express, determining the differences between vertebrates.
- 29.In a duplex circular DNA, the _____________ state has around ____________ per turn. (answer, answer)
- 30.____________is a topoisomerase II that introduces ______________ supercoiling and promote ________________. (answer, answer, answer)
- 31.A _______________ region is the same DNA sequence read either 5’ to 3’ or viceversa.
- 32.When supercoiled, the _____________number increases when there are more twists.
- 33.Part 2. Determine W, T and L respectively if DNA gyrase puts 4 negative supercoils into the 200-bp circular DNA. If relaxed, what would the value of L be?
- 34.Under which of the following conditions does the melting temp. for DNA denaturation increase?
- A.
Smaller DNA fragments
- B.
Higher G-C contents in DNA
- C.
Higher A-T contents in DNA
- D.
A and c are correct
- E.
None are correct
- 35.Which of the following statements is true about chromosomes?
- A.
They must be packed around the cell membrane.
- B.
They can exist as unwrapped DNA.
- C.
Genetic information is not located in these structures.
- D.
As part of their structure, chromatin contains histones wrapped by DNA.
- E.
None of the above.
- 36.Which of the following is not true about tRNA and rRNA?
- A.
TRNA can self-base pair forming loops and base pair with non-canonical bases
- B.
TRNA can carry at least one amino acid and contain an anticodon.
- C.
RRNA is used for ribosome assembly as large and small units that are exported to the cytosol.
- D.
RRNA can self-base pair with its complementary strand in a double stranded structure.
- E.
Ribosomes contain rRNA as well as proteins except that the former is greater in number.
- 37.The separation of a double-stranded DNA will form two template strands.
- A.
True
- B.
False
- 38.DNA replication mainly occurs in a conservative manner.
- A.
True
- B.
False
- 39.In E.coli, only one replication fork is needed to replicate a new DNA strand.
- A.
True
- B.
False
- 40.RNA can form an unstable hybrid structure with DNA.
- A.
True
- B.
False
- 41.The unwinding of DNA is an energetically favorable process to allow replication.
- A.
True
- B.
False
- 42.Template strands are only copied continuously.
- A.
True
- B.
False
- 43.In E. coli, the replication fork copies DNA continuously and segmented in a 360o direction.
- A.
True
- B.
False
- 44.DNA is unwound by gyrase without breaking it.
- A.
True
- B.
False
- 45.Eukaryotic DNA can contain more than 2 replication forks.
- A.
True
- B.
False
- 46.Replication occurs mainly during the G2 and G1 phases where cell growth occurs.
- A.
True
- B.
False
- 47.Bidirectional replication starts at the_______________, moving replication forks in opposite direction.
- 48.A_______________ is bound to Ter locus to prevent helicase activity.
- 49.High_______________means a high number of successive cycles of nucleotide addition.
- 50.A primer needed for replication is formed by a_________________.
- 51.The process in which an RNA template is transcribed to cDNA is executed by _______________.
- 52.Which of the following is true of replication?
- A.
It creates a complementary strand relying upon base-stacking interactions.
- B.
Usually, one replication fork must move 360o around the entire chromosome in E.coli.
- C.
DNA Pol I adds a new nucleotide to the 5’-end of an existing DNA molecule.
- D.
DNA Pol I adds a new nucleotide to the 3’-end of the template strand.
- E.
An antiparallel DNA strand is produced and a pyrophosphate is released.
- 53.DNA Pol III
- A.
Synthesizes Okazaki fragments.
- B.
Functions mainly in DNA repair.
- C.
Polymerizes DNA in a 5’--> 3’ direction
- D.
A and c are correct.
- E.
None of the above.
- 54.Which of the following statements is not true?
- A.
Replication occurs during the S phase of the eukaryotic cell cycle.
- B.
Helicase is an ATP-dependant protein that unwinds DNA during replication.
- C.
DNA Pol I uses its 3’--> 5’ exonuclease activity to remove primers.
- D.
Ligase seals nicks in DNA by covalently linking Okazaki fragments.
- E.
DNA Pol I has two types of exonuclease activities.
- 55.Reverse transcriptase
- A.
Can be a telomerase that uses its own RNA as template.
- B.
Is contained in all RNA tumor viruses.
- C.
Allows the transcription of cDNA from an RNA template to form a DNA:RNA hybrid.
- D.
Can be inhibited by HIV therapy.
- E.
All of the above
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