7248465
Pregunta 1
Pregunta
Match the enzymes with their function.
A. DNA polymerase I
B. DNA polymerase III
C. Primase
D. DNA ligase
E. DNA topoisomerase
F. Helicase
G. Single strand binding protein
In a newly synthesized prokaryotic DNA strand, the primers are removed by _____. [blank_start]A[blank_end]
Respuesta
-
A
Pregunta 2
Pregunta
Match the enzymes with their function.
A. DNA polymerase I
B. DNA polymerase III
C. Primase
D. DNA ligase
E. DNA topoisomerase
F. Helicase
G. Single strand binding protein
_____ synthesizes DNA during replication. [blank_start]B[blank_end]
Respuesta
-
B
Pregunta 3
Pregunta
Match the enzymes with their function.
A. DNA polymerase I
B. DNA polymerase III
C. Primase
D. DNA ligase
E. DNA topoisomerase
F. Helicase
G. Single strand binding protein
_____ require ATP to add negative supercoils to DNA. [blank_start]E[blank_end]
Respuesta
-
E
Pregunta 4
Pregunta
Patients with the rare genetic disease xeroderma pigmentosum (XP) are very sensitive to light and are highly susceptible to skin cancers. XP is caused by defective DNA repair _____.
Respuesta
-
Nucleotide excision repair
-
Mismatch repair
-
Base excision repair
-
Alkylguanine transferase
Pregunta 5
Pregunta
Match the following types of DNA damage to DNA repair system responsible for their repair.
Respuesta
-
O6-alkylguanine DNA alkyltransferase (AGT)
-
Mismatch repair (MMR)
-
Base excision repair (BER)
-
Nucleotide excision repair (NER)
Pregunta 6
Pregunta
What type of mutation most likely results from the alkylation of the oxygen on position 6 of guanine base producing O6-methylguanine?
Respuesta
-
Deletion
-
Insertion
-
Transition
-
Transversion
Pregunta 7
Pregunta
Cigarette smoking has deleterious effects on reproduction. Which of the following statements is FALSE?
Respuesta
-
Benzo[a]pyrene is not carcinogenic until it is oxidized within cells.
-
Benzo[a]pyrene diol epoxide derivatives is highly carcinogenic and mutagenic.
-
The epoxide derivatives can covalently bind to guanosine residue in DNA, to form DNA adducts.
-
The DNA adducts interrupting hydrogen bonding in G-C base pairs.
-
Base excision repair recognizes a bulky lesion and fix the repair.
Pregunta 8
Pregunta
All of the following are true about nucleotide excision repair EXCEPT:
Respuesta
-
Removal of the damaged bases occurs on only one strand of the DNA
-
It removes thymine dimers generated by UV light
-
It involves the activity of an excision nuclease, which is an exonuclease
-
It requires a polymerase and ligase
-
Only the damaged nucleotides are removed (cuts are made several nucleotides on either side of damaged bases)
Pregunta 9
Pregunta
Which of the following mechanisms does NOT affect the mutation rate due to oxidation of guanine to 8-oxo-G?
Respuesta
-
Degradation of 8-oxo-dGTP
-
Proofreading by DNA polymerase I
-
Removal of 8-oxo-G from DNA by a DNA glycosylase
-
Transfer of the oxygen to a DNA alkyl transferase
-
None of the above
Pregunta 10
Pregunta
Toxic cyanides are conjugated with:
Respuesta
-
Cysteine
-
Active sulfate
-
Glucuronic acid
-
Thiosulfate
Pregunta 11
Pregunta
Biotransformation by oxidation is catalyzed by:
Respuesta
-
Cytochrome c
-
Cytochrome aa3
-
Cytochrome b
-
Cytochrome P450
Pregunta 12
Pregunta
How would you expect DNA methylation to alter gene expression?
Respuesta
-
Extremely increase expression
-
Moderately increase expression
-
No change in expression
-
Measurably decrease expression
-
Either increase of decrease expression
Pregunta 13
Pregunta
What type of enzyme would most likely promote increased gene expression?
Respuesta
-
DNA methyltransferase
-
DNA demethylase
-
DNA polymerase
-
DNA ligase
-
DNAse
Pregunta 14
Pregunta
What characteristics of DNA allows methylation patterns to be maintained through replication and cell division?
Respuesta
-
Semiconservative replication
-
Recombination and repair
-
The absence of uracil
-
Topoisomerases
-
Deoxyribonucleotide synthesis
Pregunta 15
Pregunta
What effect does histone acetylation have on transcription?
Respuesta
-
Extremely decrease expression
-
Moderately decrease expression
-
No change in expression
-
Measurably increase expression
-
Either increase or decrease expression
Pregunta 16
Pregunta
All are characteristics of RNA-directed DNA polymerase EXCEPT:
Respuesta
-
Reverse transcriptase
-
Found in retroviruses
-
RNAse H activity
-
Synthesis polynucleotides in the 3’ to 5’ direction
Pregunta 17
Pregunta
The point where separation of the DNA occurs is called the replication fork.
Respuesta
- True
- False
Pregunta 18
Pregunta
The primers required to initiate DNA replication remain in the DNA molecule after replication.
Respuesta
- True
- False
Pregunta 19
Pregunta
The PROOFREADING activity of E. coli DNA polymerases:
Respuesta
-
Occur after DNA synthesis is complete
-
Is a function of 5’ to 3’ exonuclease activity associated with DNA polymerase itself
-
Is a function of 3’ to 5’ exonuclease activity associated with DNA polymerase itself
-
Is a function of 3’ to 5’ endonuclease activity associated with DNA polymerase itself
Pregunta 20
Pregunta
The enzyme activity inhibited by acyclovir is:
Respuesta
-
Deoxyribonuclease
-
Thymidine kinase
-
Reverese transcriptase
-
Viral DNA polymerase
Pregunta 21
Pregunta
Acyclovir:
Respuesta
-
Is a synthetic purine nucleoside analogue.
-
Must be 5’ monophosphorylated by the herpes virus thymidine kinase in order to be active.
-
Must undergo phosphorylation by cellular kinases to produce acyclovir triphosphate from acyclovir monophosphate in order to be active.
-
Results in chain termination during DNA replication because it lacks a 3’ hydroxyl group.
-
All of the above
Pregunta 22
Pregunta
The flow of genetic information in Central Dogma of Biology (included the retroviruses) is as follows:
Respuesta
-
RNA to DNA to proteins
-
RNA to DNA to RNA to proteins
-
DNA to RNA to proteins
-
DNA to RNA to DNA to RNA to proteins
Pregunta 23
Pregunta
In order for an RNA virus such as HIV to direct synthesis of new viral RNA, it must first direct synthesis of DNA. In order to do this, the virus must violate the central dogma by using an enzyme called:
Respuesta
-
Reverse translatase
-
Reverse replicase
-
Reverse transcriptase
-
Pyrophosphatase
-
Primase
Pregunta 24
Pregunta
DNA polymerase can add new nucleotides to the free _____ of a nucleotide strand.
Respuesta
-
3’-phosphate end
-
3-OH’ end
-
5’-OH end
-
3-OH’ end and 5’-OH end
-
3’-phosphate end, 3-OH’ end, and 5’-OH end
Pregunta 25
Pregunta
In a newly synthesized prokaryotic DNA strand, the primers are removed by _____.
Respuesta
-
DNA polymerase III
-
DNA ligase
-
Primase
-
DNA topoisomerase I
-
DNA polymerase I
Pregunta 26
Pregunta
DNA replicates through what process?
Respuesta
-
Conservative replication
-
Disparative replication
-
Dispersive replication
-
Semi-conversative replication
Pregunta 27
Pregunta
Zidovudine (AZT) is a more effective inhibitor of HIV reverse transcriptase than of mammalian cell DNA polymerases because:
Respuesta
-
AZT can be converted to a ribonucleotide triphosphate more efficiently than to a dTTP.
-
Mammalian DNA polymerases have a 3’ to 5’ exonuclease activity, whereas HIV reverse transcriptase does not.
-
AZT crosses the outer mammalian cell membrane more efficiently than it crosses the nuclear membrane.
Pregunta 28
Pregunta
Which of the following is NOT a function of DNA polymerase I?
Respuesta
-
5’ to 3’ exonuclease
-
3’ to 5’ exonuclease
-
Polymerase
-
Helicase
Pregunta 29
Pregunta
During replication, DNA strands separate, causing supercoiling. These supercoils are removed by:
Respuesta
-
Acid hydrolysis
-
Topoisomerases
-
Primase
-
Helicase
-
DNA polymerase I
Pregunta 30
Pregunta
An apyrimidinic or apurinic (AP) site forms in which type of DNA repair?
Respuesta
-
Photoreactivation
-
Mismatch repair
-
Direct repair
-
Nucleotide excision repair
-
Base excision repair
Pregunta 31
Pregunta
In the first step of base excision repair
Respuesta
-
A phosphodiester bond is broken
-
Two nicks are made surrounding the DNA damage
-
A break in DNA is sealed by DNA ligase
-
A base is removed by the action of a DNA glycosylase
Pregunta 32
Pregunta
What modification neutralizes the charges on histones and loosens up the interactions between histones and DNA?
Respuesta
-
Phosphorylation
-
Demethylation
-
Acetylation
-
Polyadenylation
Pregunta 33
Pregunta
DNA methylation may be a significant mode of genetic regulation in eukaryotes. Methylation refers to
Respuesta
-
Altering RNA polymerase activity by methylation of RNA polymerase
-
Alteration of DNA polymerase activity by addition of methyl groups to glycine residues
-
Addition of methyl groups to the cytosine of CG doublets
-
Altering transcription activity especially of highly methylated of daughter strands
Pregunta 34
Pregunta
Which of the following enzyme(s) excision repair?
Respuesta
-
DNA glycosylase
-
AP endonuclease
-
AP exonuclease
-
DNA glycosylase, AP endonuclease, AP exonuclease
-
DNA glycosylase and AP endonuclease
Pregunta 35
Pregunta
Which of the following is NOT TRUE of DNA methylation?
Respuesta
-
It is associated with transcription repression.
-
It occurs on cytosine adjacent to guanines
-
Cytosines on both strands are usually methylated.
-
It is carried out by DNA methyltransferases.
-
Methylation is permanent and cannot be reversed.
Pregunta 36
Pregunta
How does histone acetylation affect chromatin structure?
Respuesta
-
Neutralizes positive histone charges and binds to DNA more tightly.
-
Neutralizes negative histone charges and binds to DNA more tightly.
-
Increases positive histone charges and binds to DNA more tightly.
-
Neutralizes positive histone charges and binds to DNA more loosely.
-
Neutralizes negative histone charges and binds to DNA more loosely.
Pregunta 37
Pregunta
Nuclear receptors (estrogen receptor) belong to which class of transcription factor?
Respuesta
-
Helix-loop-helix proteins
-
Helix-turn-helix proteins
-
Leucine zipper proteins
-
Zinc finger proteins
Pregunta 38
Pregunta
Co-repressor complex has the ability to decrease histone acetylation and represses transcription.
Respuesta
- True
- False
Pregunta 39
Pregunta
Which of the following statements are FALSE?
Respuesta
-
Deamination of 5-methyl cytosine creates a G-T mismatch.
-
Transcriptionally active regions of DNA have the CpG sequence methylated.
-
DNA cytosine methylation is associated with gene silencing.
-
Deamination of cytosine creates a G-U mismatch.
Pregunta 40
Pregunta
Match the DNA damage to DNA repair system responsible for their repair (using structure attached).
Respuesta
-
Photolyase
-
Nucleotide excision repair (NER)
-
Mismatch repair (MMR)
-
O6-alkylguanine DNA alkyltransferase (AGT)
-
Base excision repair (BER)
Pregunta 41
Pregunta
Old (parental) and new (daughter) strands of DNA in bacteria can be distinguished by
Respuesta
-
DNA glycosylases
-
Methylation patterns
-
3’ to 5’ exonuclease activity
-
AP endonucleases
Pregunta 42
Pregunta
The reposition of helix-12 by estrogens (estradiol) creates an activation function (AF)-2 surface that allows the binding of coactivators LxxLL recognition site.
Respuesta
- True
- False
Pregunta 43
Pregunta
When the base cytosine undergoes deamination, it becomes
Respuesta
-
Uracil
-
Adenine
-
Guanine
-
Phosphorylated
Pregunta 44
Pregunta
E. coli DNA pol I has all of the following characteristics EXCEPT:
Respuesta
-
5’ to 3’ exonuclease activity
-
3’ to 5’ exonuclease activity
-
5’ to 3’ DNA polymerase activity
-
Does not require a primer for initiation
Pregunta 45
Pregunta
Which of the following description about topoisomerases (gyrases) is FALSE?
Respuesta
-
They break and reseal phosphodiester bond.
-
They form covalent intermediates with their DNA substrates.
-
The chemical bond between a tyrosyl residue and a phosphoryl group in topoisomerase I is irreversible.
-
Topoisomerase II use ATP to form negatively supercoiled DNA to overcome the torsion stress imposed upon unwinding.
Pregunta 46
Pregunta
AZT, is the first approved HIV drug. Which of the following statements about AZT are TRUE?
I. AZT is phosphorylated by cellular thymidine kinase to form AZT-monophosphate.
II. AZT-monophosphate is further phosphorylated by cellular kinases to form AZT-triphosphate.
III. AZT-triphosphate is a substrate for DNA polymerase, incorporated into growing polynucleotide chains in the place of adenosine residues.
Respuesta
-
I
-
II
-
I and II
-
I, II and III
Pregunta 47
Pregunta
A ten-year old girl is brought to the dermatologist by her parents. She has many freckles on her face, neck, arms, and hands, and the parents report that she is usually sensitive to sunlight. Two basal cell carcinomas are identified on her face. Which of the following processes is most likely to be defective in this patient?
Respuesta
-
Repair of double-strand breaks.
-
Removal of mismatched bases from the 3’-end of Okazaki fragments.
-
Removal of pyrimidine dimers from DNA.
-
Removal of uracil from DNA.
Pregunta 48
Pregunta
All of the following are true about nucleotide excision repair EXCEPT:
Respuesta
-
Removal of the damaged bases occurs on only one strand of the DNA.
-
It removes thymine dimers generated by UV light.
-
It involves the activity of an excision nuclease, which is an endonuclease.
-
It requires a polymerase and a ligase.
-
Recognizes small damaged bases in DNA (methylated and oxidized bases) and fix the repair.
Pregunta 49
Pregunta
Another type of DNA repair is base excision repair. Base excision repair
Respuesta
-
Is used only for bases that have been deaminated.
-
Uses enzymes called DNA glycosylases to generate an abasic sugar site.
-
Remove about 10 to 15 nucleotides.
-
Recognizes a bulky lesion.
-
Does not require an endonuclease.
Pregunta 50
Pregunta
Cigarette smoking has deleterious effects on reproduction. Which of the following statements is FALSE?
Respuesta
-
Benzo[a]pyrene is not carcinogenic until it is oxidized within cells.
-
Benzo[a]pyrene diol epoxide derivatives is highly carcinogenic and mutagenic.
-
The reactive molecules react with adenine nucleotides to cause DNA damage.
-
The DNA adducts interrupting hydrogen bonding in G-C base pairs.
Pregunta 51
Pregunta
Mutation in DNA may result from all of the following EXCEPT:
Respuesta
-
Spontaneous mutations due to errors in replication.
-
Physical insults on the cell, such as UV light.
-
Chemical mutagens
-
Introduction of a base analog into DNA.
-
Errors in transcription.
Pregunta 52
Pregunta
Tamoxifen is a selective estrogen receptor modulator, has been approved by the FDA for use in the treatment of breast cancer. Which of the following statements is FALSE?
Respuesta
-
Tamoxifen can prevent breast cancer by acting as an antagonist.
-
Tamoxifen crosses the cell membranes and binds to estrogen receptors.
-
Binding of tamoxifen to estrogen receptor induces a conformational change, which can inhibit the binding of a coactivator.
-
The reposition of helix-12 by tamoxifen creates an activation function AF-2) surface that allows the binding of coactivators.
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