BIO Practice from Practice Exam 2|112 Questions with Verified Answers
Complementary base-pairing allows for
A) genes to be expressed as phenotype.
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B) spontaneous mutations to occur.
C) covalent bonds to form between the opposite bases.
D) replication to be semiconservative.
E) DNA to serve as its own template for replication. - CORRECT ANSWER E) DNA to serve as its own template for replication.
6) The process by which genetic information is transferred from DNA to RNA is called
A) translation.
B) transcription.
C) transversion.
D) replication.
E) transformation. - CORRECT ANSWER B) transcription.
8) After a region of DNA has been replicated, ______ removes the RNA primers.
A) DNA helicase
B) DNA polymerase I
C) DNA ligase
D) DNA polymerase III
E) RNA primase - CORRECT ANSWER B) DNA polymerase I
10) Which genetic disease(s) are caused by defective proteins that are not enzymes?
A) Albinism and alkaptonuria
B) Tay-Sachs disease and phenylketonuria
C) Lesch-Nyhan syndrome.
D) Sickle-cell anemia and cystic fibrosis
E) All of these - CORRECT ANSWER D) Sickle-cell anemia and cystic fibrosis
11) A person with sickle-cell trait has ________ at the beta-globin locus. A) one mutant and one deleted allele
B) one wild-type and one deleted allele
C) two wild-type alleles
D) two mutant alleles
E) one wild-type and one mutant allele - CORRECT ANSWER E) one wild-type and one mutant allele
What is a replication bubble?
A) A DNA sequence that initiates replication
B) A locally denatured segment of DNA where replication originates C) A tangle of denatured DNA strands near the replication fork
D) A localized site in the nucleus where chromosomes are replicating E) A complex of replication enzymes on the DNA template strand - CORRECT ANSWER B) A locally denatured segment of DNA where replication originates
During replication, the direction of synthesis of new DNA from the leading and lagging strands is
A) from left to right only.
B) 5' to 3' only.
C) 3' to 5' only.
D) both 5' to 3' and 3' to 5'.
E) different, depending on whether the cell is prokaryotic or eukaryotic. - CORRECT ANSWER B) 5' to 3' only.
As helicase unwinds the DNA molecule, what keeps the strands apart?
A) DNA polymerase
B) Single-strand binding proteins
C) Reverse transcriptase
D) Okazaki fragments
E) Replication fork - CORRECT ANSWER B) Single-strand binding proteins
In eukaryotes, where does transcription take place?
A) In both the cytoplasm and nucleus
B) In the mitochondrion
C) In the nucleus
D) Anywhere in the cell
E) In the cytoplasm - CORRECT ANSWER C) In the nucleus
The sequence of bases of a molecule of mRNA is converted into a corresponding amino acid sequence during
A) translation.
B) replication.
C) transversion.
D) transcription.
E) transformation. - CORRECT ANSWER A) translation
How many replication forks are produced when DNA denatures at an origin?
A) 3
B) The number varies
C) 0
D) 1
E) 2 - CORRECT ANSWER E) 2
What does a gene actually code for?
A) A protein
B) An amino acid
C) A nucleotide
D) A polypeptide
E) An enzyme - CORRECT ANSWER D) A polypeptide
Which enzyme elongates the new DNA strand starting at an RNA primer?
A) DNA polymerase III
B) DNA polymerase I
C) RNA polymerase
D) DNA ligase
E) RNA primase - CORRECT ANSWER A) DNA polymerase III
During the initiation step of transcription, what molecule binds the promoter region of a DNA molecule?
A) RNA polymerase
B) DNA primase
C) Topoisomerase
D) DNA polymerase
E) Reverse transcriptase - CORRECT ANSWER A) RNA polymerase
After removal of the RNA primers and replacement with DNA nucleotides, the single-stranded nick adjacent to Okazaki fragments is filled in through a reaction that involves which enzyme?
A) DNA ligase
B) SSB protein
C) DNA helicase
D) DNA primase
E) RNA polymerase - CORRECT ANSWER A) DNA ligase
Among Caucasians, the most common lethal autosomal recessive disease is
A) sickle-cell disease.
B) muscular dystrophy.
C) hemophilia.
D) cystic fibrosis.
E) phenylketonuria. - CORRECT ANSWER D) cystic fibrosis.
Which event occurs at the termination of transcription?
A) RNA polymerase is released from the DNA.
B) RNA synthesis stops.
C) The RNA chain is released from the DNA.
D) Both A and C
E) All of the above - CORRECT ANSWER E) All of the above
In both prokaryotes and eukaryotes, DNA replication is
A) bidirectional and semiconservative.
B) bidirectional and dispersive.
C) unidirectional and semiconservative.
D) unidirectional and dispersive.
E) dispersive and semiconservative. - CORRECT ANSWER A) bidirectional and semiconservative.
Which enzyme activity is associated with DNA polymerase I?
A) 5' to 3' polymerase
B) 3' to 5' exonuclease
C) 5' to 3' exonuclease
D) Both A and B
E) All of the above - CORRECT ANSWER E) All of the above
Only the leading strand of a DNA molecule serves as a template during replication.
True or False - CORRECT ANSWER False
Okazaki fragments are made from the lagging strand of the DNA double helix.
True or False - CORRECT ANSWER True
A promoter is a coding portion of a gene.
true or false - CORRECT ANSWER False
As replication proceeds, the lagging strand of DNA is looped back on itself so that it has the same orientation as the leading strand template; the looped DNA repeatedly grows and shortens during lagging strand replication. This model is often referred to as the _________. - CORRECT ANSWER trombone model
RNA polymerase moves along the template strand of DNA in the ____ direction, and adds nucleotides to the ____ end of the growing transcript. - CORRECT ANSWER 3' to 5'; 3'
What must the mismatch repair system be able to distinguish in order to tell which nucleotide of a mismatched pair to replace?
a. It must be able to distinguish which chain possesses the right sequence.
b. It must be able to distinguish the newly made strand from the parental strand.
c. It must be able to distinguish which chain is of the right polarity.
d. It must be able to distinguish which chain contains more incorrect bases.
e. all of the above - CORRECT ANSWER b. it must be able to distinguish between the newly made strand and from the parental strand
Many of the RNA polymerase II promoters are TATA-less but they are still recognized by the same specific GTF in a sequence specific manner. These promoters must contain ______ plus DPE or DCE that are all recognized by a _______ subunit of ________. - CORRECT ANSWER Inr/TAF/ TFIID
Which of the following statements best describes the termination of transcription in prokaryotes?
a. RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene
and release the mRNA.
b. RNA polymerase transcribes through the terminator sequence, causing the polymerase to fall off the DNA and
release the transcript.
c. RNA polymerase transcribes through an intron, and the splicing machinery causes the polymerase to let go of the
transcript.
d. Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome.
e. RNA polymerase transcribes through the polyadenylation signal, causing proteins to associate with the transcript
and cut it free from the polymerase. - CORRECT ANSWER b. RNA polymerase transcribes through the terminator sequence, causing the polymerase to fall off the DNA and release the transcript
Transcribe the following sequence: 5' - TCTAGGC- 3'? - CORRECT ANSWER 5' - GCCUAGA - 3'
Extension of the lagging strand template at vertebrate telomeres occurs by a process that could be termed as
a. replication
b. reverse transcription
c. termination
d. translation
e. transcription - CORRECT ANSWER b. reverse transcription
How does active CRP (or CAP) induce expression of the genes of the lac operon?
a. It terminates production of repressor molecules.
b. It degrades the substrate lactose.
c. It stimulates splicing of the encoded genes.
d. It stimulates the binding of RNA polymerase to the promoter.
e. It binds steroid hormones and controls translation - CORRECT ANSWER d. It stimulates binding of the RNA polymerase to the promoter
Which of the following is characteristic of the lytic cycle?
a. Many bacterial cells containing viral DNA are produced.
b. Viral DNA is incorporated into the host genome.
c. The viral genome replicates without destroying the host.
d. New phages are produced and released while killing the host.
e. The virus-host relationship usually lasts for generations. - CORRECT ANSWER d. New phages are produced and released while killing the host
Which of the following is a type of cis-acting element primarily "acting" in RNA rather than DNA?
a. promoter
b. "up" element
c. intrinsic transcription terminator
d. operator
e. both c and d - CORRECT ANSWER c. intrinsic transcription terminator
Considering a typical prokaryotic or eukaryotic cell what is the most abundant type of RNA?
a. mRNA
b. tRNA
c. rRNA
d. miRNA
e. snRNA - CORRECT ANSWER c. rRNA
One of the factors that may affect initiation of DNA replication in E. coli
a. the acetylation state of histones at oriC
b. the acetylation state of A's at oriC
c. the methylation state of A's at oriC
d. the methylation state anywhere on the chromosome
e. the methylation state of T's at ARS - CORRECT ANSWER c. The methylation state of A's at oriC
DNA is composed of two strands, only one of which typically is used as a template for RNA synthesis. By what mechanism is the correct strand chosen?
a. Both strands are tried and the one that works is remembered.
b. Only one strand has the start codon.
c. The promoter acts to aim (position) the RNA polymerase.
d. A start factor informs the system.
e. It is chosen randomly. - CORRECT ANSWER c. The promoter acts to aim (position) the RNA polymerase
There is a large class of DNA polymerases that are specialized for incorporating nucleotides opposite various types of DNA lesions in the template strand. They engage in a type of DNA synthesis called __________. They usually do not possess ______________ activity that is characteristic of most other DNA polymerases.
a. translational synthesis/ a helicase
b. translesion synthesis/ a 3' to 5' exonuclease
c. transdimensional synthesis/ a polymerase
d. translesion synthesis/ a ligase
e. transliteral synthesis/ a 5' to 3' exonuclease - CORRECT ANSWER b. translesion synthesis/ a 3' to 5' exonuclease
If antitermination is utilized to regulate gene expression, this mechanism enables __________.
a. promoters to function as a terminator
b. terminator to function as a promoter
c. RNA polymerases to initiate transcription using a new (different) set of promoters
d. RNA polymerases to read through the transcription terminators
e. RNA polymerases to terminate at a new set of promoters - CORRECT ANSWER d. RNA polymerases to read through the transcription terminators
Which of the following is not an activity of bacterial core RNA polymerase or any of the eukaryotic RNAPs (I-III)?
a. unwinding and rewinding of DNA
b. catalyzing addition of ribonucleotides
c. recognition of promoters
d. holding a newly synthesized portion of RNA product
e.holding separated DNA strands - CORRECT ANSWER c. recognition of promoters
Which of the following statements about transcription regulation is incorrect?
a. In negative control the default state is "on" unless a repressor binds the operator (n prokaryotes) and turns the
gene off.
b. The binding of a repressor protein blocks or reduces transcription
c. Some repressor proteins require the presence of a corepressor molecule in order to bind an operator
d. In positive control the default state is "off" and the transcription is activated to above the basal level only when
the activator is bound to its binding element (site).
e. In positive control an activator always binds the operator and allows RNA polymerase to initiate transcription - CORRECT ANSWER e. In positive control an activator always binds the operator and allows RNA polymerase to initiate transcription.
Which type of DNA repair involves the preferential repair of strands of genes that are actively serving as templates for RNA synthesis?
a. transcription-coupled pathway
b. global pathway
c. base excision repair
d. nucleotide excision repair
e. a and d - CORRECT ANSWER e. a and d (transcription-coupled pathway and nucleotide excision repair)
Here is a diagram of DNA replication in E.coli. The darker strands are newly synthesized, #1 points to the new strand in the top duplex and #4 in the bottom duplex.
1) The hexametric protein complex indicated by #5 is a ________. It uses _______ as an energy source.
2) The sliding clamp (beta clamp) would be found associated with structure # ___________ and greatly increases its processivity.
3) #3 indicates __________ that is a single polypeptide protein with several enzymatic activities. One of these activities is a ___________ that could be used in nick translation to label double-stranded DNA molecules.
4) #3 indicates a single polypeptide protein with several enzymatic activities. One of these activities is a _____ that is used for primer removal and the other is _________ used for proofreading
5) The sliding clamp (beta clamp) would be found associated with structure # ___________ and greatly increase its - CORRECT ANSWER 1) helicase/ ATP
2) 2
3) DNA polymerase I/ 5' to 3' exonuclease activity
4) 5' to 3' exonuclease activity; 3' to 5' exonuclease activity
5) two/ processivity
6) six
7) Primase
The 5' end of each Okazaki fragment begins with:
a. the same RNA primer that began synthesis on the leading strand.
b. a DNA primer binding to the template DNA.
c. DNA polymerase binding to the template DNA.
d. a separate RNA primer.
e. a small DNA primer. - CORRECT ANSWER d. a separate RNA primer
Which of the following statements best describes the termination of transcription in eukaryotes by RNA Pol II?
a. RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene
and release the mRNA.
b. RNA polymerase transcribes through the terminator sequence, causing the polymerase to fall off the DNA and
release the transcript.
c. RNA polymerase transcribes through the polyadenylation signal, causing proteins to associate with the transcript
and cut it free from the polymerase, which continues to synthesize more "nonfunctional" RNA.
d. Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome.
e. It may be a, b or c. depending on a gene. - CORRECT ANSWER c. RNA polymerase transcribes through the polyadenylation signal, causing proteins to associate with the transcript and cut it free from the polymerase, which continues to synthesize more "nonfunctional" RNA
Which of the following is false about nuclear genes for the 3 largest rRNAs in higher eukaryotes?
a. they are transcribed in the nucleolus
b. each "gene" is transcribed into a large precursor RNA that needs to be cut and trimmed to give rise to 3 mature rRNAs
c. they are transcribed by RNA Pol I
d. they are translated into r-proteins in the cytoplasm
e. none of the above is false; all are true - CORRECT ANSWER d. they are translated into r-proteins in the cytoplasm
The function of eukaryotic telomerase is to
a. synthesize DNA primers at the end of each chromosome.
b. extend the lagging strand to the end of each chromosome.
c. extend the lagging strand template at the end of each chromosome.
d. finish the synthesis of the leading strand at the end of each chromosomes
e. extend the leading strand template at the end of each chromosome. - CORRECT ANSWER c. extend the lagging strand template at the end of each chromosome
In eukaryotic cells, a complex of proteins binds to the broken ends (ds breaks) of the DNA duplex and catalyzes a series of reactions that rejoin the broken strands by a process that usually results in some DNA loss. This is an example of what kind of repair?
a. nucleotide excision repair
b. base excision repair
c. homologous recombination
d. non homologous end joining
e. single-strand breakage repair - CORRECT ANSWER d. non-homologous end joining
Which of the following is false?
a. RNA polymerase I (generally) requires only two ancillary factors for efficient initiation of transcription
b. RNA polymerase I requires TBP for initiation of transcription
c. RNA polymerase I transcribes 5S rRNA
d. RNA polymerase I promoters are bipartite consisting of core promoter and UCE
e. None of the above - CORRECT ANSWER c. RNA polymerase I transcribes 5S rRNA
Which of the following statements is false when comparing prokaryotes with eukaryotes?
a. The prokaryotic chromosome is usually circular, whereas eukaryotic nuclear chromosomes are linear.
b. Prokaryotic chromosomes usually have a single origin of replication, whereas eukaryotic chromosomes have many.
c. The rate of elongation during DNA replication is higher in prokaryotes than in eukaryotes.
d. Prokaryotes produce longer Okazaki fragments during DNA replication than eukaryotes.
e. The ends of eukaryotic and prokaryotic chromosomes comprise telomeres. - CORRECT ANSWER The ends of eukaryotic and prokaryotic chromosomes comprise telomeres
Statement A. Prokaryotic intrinsic transcription terminators consist of two features that are both required for termination to occur: a hairpin that is followed by a run of U's
Statement B. Eukaryotic RNA Pol. I and III terminate transcription right after specific terminator sequences are transcribed similarly to prokaryotic RNA Pol. - CORRECT ANSWER Both A and B are true
Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight because their cells have an impaired ability to
a. replicate DNA by translesion polymerases.
b. repair chromosomal breaks.
c. correct mismatches generated during replication
d. remove pyrimidine dimers by NER pathway - CORRECT ANSWER d. Remove pyrimidine dimers by NER pathway
Which of the following is/are true?
a. RNAP III can initiate at its promoters in the absence of any additional factors
b. RNAP III promoters usually contain positions that lie downstream of the startpoint
c. RNAP III functions primarily within the nucleolus
d. all of the above
e. b. and c. only - CORRECT ANSWER b. RNAP II promoters usually contain positions that lie downstream of the start point
Which of the following statements about mammalian telomeres is incorrect?
a. They all contain multiple copies of a short DNA sequence that is specific for each organism.
b. They may protect chromosomes from degradation.
c. They can be extended by an enzyme called telomerase that carries an RNA molecule that is complementary to
the telomeric repeats.
d. They may protect the cell from chromosomal fusions.
e. None of the above. - CORRECT ANSWER e. None of the above, they are all correct
Transcription involves synthesis of an RNA chain representing one strand of a DNA duplex. The strand that has the "same" sequence as the RNA product is the ________ strand and the one with the complementary sequence (to RNA) is the ________ strand
a. antisense/sense
b. sense/antisense
c. coding/template
d. nontemplate/noncoding
e. both b and c - CORRECT ANSWER e. b and c (sense/antisense and coding/template)
What happens when the DNA polymerase on the lagging strand template completes the synthesis of an Okazaki fragment?
a. It disengages from the beta clamp.
b. It binds more tightly to the beta clamp.
c. It cycles to a new beta clamp that has been assembled at an RNA primer-DNA template junction closer to the
replication fork.
d. It cycles to a new beta clamp that has been assembled at an RNA primer-DNA template junction farther from the replication fork.
e. a and c - CORRECT ANSWER e. a and c
(It disengages the beta clamp; it cycles to a new beta clamp that has been assembled at an RNA primer-DNA template junction closer to the replication fork)
Many of the RNA polymerase II promoters contain ______, an element generally present at a "fixed" distance upstream from startpoint. When present, this element is bound by ________ via its subunit called _________. - CORRECT ANSWER TATA box/ TFIID/ TBP
In order to create the replication forks (initiate DNA replication) in E.coli, oriC needs to be "activated". The first step in this process involves binding of _______ proteins to oriC and melting of short stretches of DNA before other proteins can join the complex. During DNA replication ________ protein is required only at oriC.
a. DnaA
b. DnaB
c. DnaC
d. DnaG
e. SSB - CORRECT ANSWER a. DnaA
Why do eukaryotic cells have multiple initiation sites in their DNA unlike bacteria that usually have only one?
a. Cells of higher organisms can have up to 1000 times the amount of DNA as bacteria.
b. Eukaryotic cells incorporate nucleotides at much slower rates.
c. Eukaryotic DNA sequences are much more complicated.
d. Eukaryotic cells have too many DNA polymerases
e. a and b - CORRECT ANSWER e. a and b
(Cells of higher organisms can have up to 1000 times the amount of DNA as bacteria; Eukaryotic cells incorporate nucleotides at much slower rates)
Place the steps in base excision repair (BER) in the correct order.
1 - Damaged base is removed by cleavage of glycosidic linkage attaching it to deoxyribose.
2 - Baseless deoxyribose phosphate in site is excised by a specialized AP endo/exonuclease.
3 - DNA glycosylase recognizes specific altered base.
4 - The strand is sealed by DNA ligase.
5 - Gap is filled by DNA polymerase; it inserts a nucleotide complementary to the undamaged strand. - CORRECT ANSWER 3. DNA glycosylase recognizes specific altered base
1. Damaged base is removed by cleavage of glycosidic linkage attaching it to deoxyribose
2. Baseless deoxyribose phosphate is site is excised by a specialized AP endo/exonuclease
5. Gap is filled by DNA polymerase; it inserts a nucleotide complementary to the undamaged strand
4. The strand is sealed by DNA ligase
Statement A. The activation of origins of replication is very similar in all organisms and requires sequence-specific binding of initiator proteins, meting of AT rich region by initiators that is followed by recruitment of replication machinery.
Statement B. At all origins of replication helicases are loaded, by helicase loaders, directly onto single stranded DNA generated by the initiators. - CORRECT ANSWER Both A and B are FALSE
Which of the following is false about the E. coli general sigma factor ( σ70)?
a. it contacts promoter directly at -10 and -35
b. mutations in sigma may suppress mutations in promoters
c. removal of C-terminus allows sigma (alone) to bind promoters
d. It has several DNA binding domains
e. none of the above - CORRECT ANSWER c. Removal of C-terminus allows sigma (alone) to bind promoters
If the position of a nucleotide (base) in (or near) a transcription unit is assigned the value of 0 (zero), this base is?
a. the startpoint of replication
b. the startpoint of transcription
c. the startpoint of translation
d. the end point of transcription
e. none of the above because bases are never assigned a value of 0 (zero) - CORRECT ANSWER e. None of the above because bases are never assigned a value of 0 (zero)
One of the RNA polymerase I ancillary factors, SL1, consists of four proteins. One of its component proteins is also required for the initiation by RNA polymerase II and RNA polymerase III as a part of a "positioning" factor. This protein common to all three "positioning" factors is called _______.
a. TFIID
b. TBP
c. TFIIIB
d. UBF1
e. PABP - CORRECT ANSWER b. TBP
Which of the following is false about bacterial RNA polymerase catalyzed reactions (synthesis of RNA)?
a. dNTPs act as substrates
b. new nucleotides are always added at the 3' end
c. these reactions occur at the catalytic site located in the sigma subunit
d. they can occur in the absence of sigma
e. both a. and c. are false - CORRECT ANSWER e. both a and c are false
(dNTPs act as substrates= FALSE)
(these reactions occur at the catalytic site located in the sigma subunit=FALSE)
Which protein/enzyme is used to decatenate E. coli chromosomes after replication?
a. DNA pol
b. Telomerase
c. Topoisomerase
d. Ligase
e. Helicase - CORRECT ANSWER c. Topoisomerase
Bacterial RNA polymerase passes through several steps prior to elongation. These steps include
1. release or change of association with sigma,
2. formation of an open binary complex.
3. formation of a closed binary complex.
4. abortive initiation.
5. promoter clearance.
The correct sequence of events is: - CORRECT ANSWER 3. Formation of a closed binary complex
2. Formation of an open binary complex
4. Abortive initiation
1. Release or change of association with sigma
5. Promoter clearance
Before RNA polymerase II can leave the promoter its CTD needs to be phosphorylated by the _____activity of ___. - CORRECT ANSWER kinase/ TFIIH
Alternative sigma factors are used as a means to regulate gene expression in bacteria. A replacement of one sigma factor for another on bacterial RNA polymerase will enable __________ .
a. a promoter to function as a terminator
b. a terminator to function as a promoter
c. RNA polymerases to initiate transcription using a new (different) set of promoters
d. RNA polymerase to read through transcription terminators
e. RNA polymerase to terminate at a new set of terminators - CORRECT ANSWER c. RNA polymerase to initiate transcription using a new (different) set of promoters
Concerning the promoters recognized by general sigma factor (σ70) in E. coli, mutations in the -35 region tend to affect the formation of the _____complexes and the mutations in the -10 region affect the formation of the _____complexes. - CORRECT ANSWER closed/ open
A eukaryotic cell lacking a telomerase activity would
a. have a high probability of becoming cancerous.
b. not be able to repair Okazaki fragments.
c. never be able to divide.
d. undergo a reduction in chromosome length during each cell cycle.
e. All of the above - CORRECT ANSWER d. undergo a reduction in chromosome length during each cell cycle
Statement A. In eukaryotes the pre-replicative complex (pre-RC) can be formed only during M but it remainsinactive until the onset of S phase.
Statement B. The ability to form pre-RCs or activate them during different stages of the cell cycle is controlled by the level of activity of Cdk (cyclin dependent kinase) - CORRECT ANSWER only statement B is true
Which of the following strategies is not used by phages to organize the expression of their genes into regulatory cascades?
a. successive alternative sigma factors
b. phage specific RNA polymerases
c. antitermination proteins
d. successive alternative ribosomes
e. all of the above may be used by different phages - CORRECT ANSWER d. successive alternative ribosomes
A specific prokaryotic transcription unit that is 5,000 nucleotides long uses only 1,200 nucleotides to make a protein consisting of 400 amino acids. This is best explained by the fact that
a. it may contain several introns that are spliced out
b. there is redundancy and ambiguity in the genetic code
c. many nucleotides may be present within the 5' and 3' UTR's
d. nucleotides break off and are lost during or after the transcription process
e. a and c - CORRECT ANSWER c. many nucleotides may be present within the 5' and 3' UTR's
Which of the following statements about telomerase is incorrect?
a. It is a DNA polymerase that generates single-stranded DNA
b. It is a reverse transcriptase
c. It does not require a primer
d. It does not require a template at the end of the chromosome because it carries its own template in the form of RNA
e. none the above - CORRECT ANSWER d. It does not require a template at the end of the chromosome because it carries its own template in the form of RNA
Which of the following statements about telomerase is incorrect?
a. It is a DNA Polymerase that generates a single stranded DNA.
b. It is a reverse transcriptase.
c. It requires a primer.
d. It does not require a template at the end of the chromosome because it carries its own template.
e. None of the above. - CORRECT ANSWER e. None of the above
An eukaryotic cell lacking a telomerase activity would
a. have a high probability of becoming cancerous.
b. not be able to repair Okazaki fragments.
c. never be able to divide.
d. all of the above
e. none of the above - CORRECT ANSWER e. non of the above
Assume that the following single strand of DNA was synthesized using standard dA TP , dGTP , dCTP , and dTTP
precursors; however, the innermost phosphate (alpha phosphate) of all the dGTPs was labeled with 32P.
3'—CT AGT AGCTT A—5'
Assume also that the strand was degraded to completion by the enzyme spleen diesterase. Spleen diesterase cleaves DNA at the covalent bond that connects the 5' carbon of the sugar to the phosphate. Which of the resulting nucleotide(s) might now carry the 32P? - CORRECT ANSWER C and T
Which of the following statements about mammalian telomeres is incorrect?
a. They all contain multiple copies of a short DNA sequence that is specific for each organism.
b. They may protect chromosomes from degradation.
c. They can be extended by an enzyme called telomerase that carries a DNA molecule that is complementary to the
telomeric repeats
d. they may protect the cell from chromosomal fusion
e. None of the above - CORRECT ANSWER c. They can be extended by an enzyme called telomerase that carries a DNA molecule that is complementary to the telomeric repeats
8-OxoG may be generated by ______ and this modified base has a tendency to pair with A. Therefore if it is not repaired prior to replication its presence in DNA would lead to _________.
a. oxidation/transitions
b. deamination/transverison
c. alkylation/transitions
d. oxidation/transversions
e. alkylation/transversions - CORRECT ANSWER d. oxidation/transversions
Which of the following is false about A-form double helices?
a. they are left handed with ~ 11 bp/turn
b. they are a typical confirmation of all nucleic acids under physiological conditions
c. they are never found in nature
d. all of the above
e. a. and b. only - CORRECT ANSWER d. all of the above statements are false about A-form double helices
Which of the following could have an effect on initiation of DNA replication in E. coli?
a. binding of secA at oriC
b. binding of ORC to oriC
c. the methylation state at oriC
d. all of the above
e. a and c only - CORRECT ANSWER e. a and c only
(binding of secA at oriC and the methylation state at oriC)
Which of the following is analogous to telomeres?
a. the pull tab on a soft drink can
b. the two ends of a shoelace
c. the central spindle of a CD that fits around while in the case
d. the mechanism of a zipper that allows the separated parts to be joined
e. the correct letters used to replace errors in a document after they have been deleted in a word processor - CORRECT ANSWER b. the two ends of a shoelace
Water can be DNA's "enemy" by participating in all of the following reactions except:
a. Hydrolysis generating AP sites (abasic).
b. Deamination of Cs converting them to Us.
c. Deamination of 5 methyl Cs converting them to Ts.
d. Deamination of Ts converting them to Cs
e. None of the above - CORRECT ANSWER d. Deamination of T's converting them to C's
Which one of the following is not directly involved in mismatch repair in E.coli?
a. MutS
b. DNA Polymerase
c. MutH endonuclease
d. methyltransferase
e. exonuclease - CORRECT ANSWER d. methyltransferase
1) The structures best represented by the letter E (black and white portions are?
2) The correct designation for the structure or position labelled A could be? - CORRECT ANSWER 1) composed of RNA and DNA
2) a primer
The best term to describe the extension of the lagging strand template of vertebrate telomeres is?
a. DNA replication
b. termination
c. reverse transcription
d. transcription
e. reverse replication - CORRECT ANSWER c. reverse transcription
In eukaryotic cells, a complex of proteins binds to broken ends (ds breaks) of the DNA duplex and catalyzes a series of reactions that rejoin the broken strands by a process that usually results in some DNA loss. This is an example of what kind of repair?
a. nucleotide excision repair
b. base excision repair
c. homologous recombination
d. non homologous end joining
e. single-stranded breakage repair - CORRECT ANSWER d. non homologous end joining
Why do eukaryotic cells have multiple initiation sites in their DNA unlike bacteria that usually have only one?
a. Cells of higher organisms can have up to 1000 times the amount of DNA as bacteria.
b. Prokaryotic cells incorporate nucleotides at much slower rates.
c. Eukaryotic Okazaki fragments are ~10X shorter.
d. all of the above
e. a. and c. only - CORRECT ANSWER e. a and c only
(more DNA than bacteria; Eukaryotic Okazaki fragments are ~10 times shorter)
Nick translation where a part of one DNA strand is replaced by a new strand (e.g. incorporating labeled nucleotides to generate radioactive or fluorescent probes) requires the following enzymatic activities:
a. DNA polymerase adding new nucleotides to the 5' end and 3' to 5' exonuclease activity for "old" strand
degradation
b. DNA polymerase adding new nucleotides to the 5' end followed by ligase activity
c. DNA polymerase adding new nucleotides to the 3' end and 5' to 3' exonuclease activity for "old" strand
degradation
d. Primase activity followed by DNA polymerase adding new nucleotides to the 5' end
e. DNA polymerase adding new nucleotides to the 3' end and 3' to 5' exonuclease activity for "old" strand
degradation - CORRECT ANSWER c. DNA polymerase adding new nucleotides to the 3' end and 5' to 3' exonuclease activity for "old" strand
Place the steps in base excision repair (BER) in the correct order.
1 -A base is removed by cleavage of glycosidic linkage attaching it to deoxyribose.
2 - Baseless deoxyribose is recognized by AP endo/nuclease that created a nick in one strand.
3 - DNA glycosylase recognizes a specific base.
4 - The nick is sealed by DNA ligase.
5 - DNA polymerase inserts one or several nucleotides using a nick as a primer. - CORRECT ANSWER 3. DNA glycosylase recognizes a specific base
1. A base is removed by cleavage of glycosidic linkage attaching it to deoxyribose
2. Baseless deoxyribose is recognized by AP endonuclease that created a nick in one strand
5. DNA polymerase inserts one or several nucleotides using a nick as a primer
4. The nick is sealed by DNA ligase
RNA polymerase and DNA polymerase differ in that
a. RNA polymerase uses RNA as a template, and DNA polymerase uses a DNA template.
b. RNA polymerase binds to single-stranded DNA, and DNA polymerase binds to double-stranded DNA.
c. RNA polymerase is much more accurate than DNA polymerase.
d. RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis.
e. RNA polymerase does not need to separate the two strands of DNA in order to synthesize an RNA copy, whereas DNA polymerase must unwind the double helix before it can replicate the DNA. - CORRECT ANSWER d. RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis
Which DNA repair mechanism removes single nucleotides altered by reactive chemicals that may be present in the diet or be produced by metabolism? Such alterations are recognized by enzymes called glycosylases.
a. nucleotide excision repair
b. base excision repair
c. mismatch repair
d. double-strand breakage repair
e. all of the above - CORRECT ANSWER b. base excision repair
Which of the following mechanisms can correct and remove/repair pyrimidine dimers in humans?
a. photoreactivation
b. NER
c. translesion synthesis
d. all of the above
e. b and c only - CORRECT ANSWER b. NER
In order to create the replication forks (initiate DNA replication) in E.coli, oriC needs to be "activated". The firststep in this process involves binding of _______ proteins to oriC and melting of short stretch of DNA before other proteins can join the complex. This protein is referred to as the __________.
a. DnaX/replicator
b. DnaA/initiator
c. DnaB/helicase loader
d. DnaC/helicase
e. DnaD/primase - CORRECT ANSWER b. DnaA/initiator
Every organism has several different DNA polymerases. There are several families of DNA polymerases that are involved in __________ which involves addition of nucleotides across abasic sites or damaged/abnormal bases. These enzymes usually not capable of proofreading, which depends on __________ activity.
a. translational synthesis/a 3' to 5' exonuclease
b. translesion synthesis/a 5' to 3' exonuclease
c. translesion synthesis/a ligase
d. translesion synthesis/a 3' to 5' exonuclease
e. translational synthesis/a 5' to 3' exonuclease - CORRECT ANSWER d. tranlesion synthesis/a 3' to 5' exonuclease
Which of the following may contribute to stabilizing the 2D and/or 3D structures of RNA?
a. hydrogen bonding via 2'OH group
b. base stacking
c. G-U base pairing
d. all of the above
e. a and b only - CORRECT ANSWER d. all of the above
(hydrogen bonding via 2'OH group
base stakcing
G-U base pairing)
The function of eukaryotic telomerase is to
a. synthesize DNA primers at the end of each chromosome.
b. extend the lagging strand to the end of each chromosome.
c. extend the leading strand template at the end of each chromosome.
d. extend the leading strand at the end of each chromosomes
e. extend the lagging strand template at the end of each chromosome. - CORRECT ANSWER e. extend the lagging strand template at the end of each chromosome
The 5' end of each Okazaki fragment begins with:
a. the same RNA primer that began synthesis on the leading strand.
b. a DNA primer binding to the template DNA.
c. DNA polymerase binding to the template DNA.
d. a separate RNA primer.
e. a small DNA primer. - CORRECT ANSWER d. a separate RNA primer
Which type of DNA repair involves the preferential repair of strands of genes that are actively serving as templates for RNA synthesis?
a. transcription-coupled repair (TCR)
b. non-homologous end joining (NHEJ)
c. base excision repair (BER)
d. nucleotide excision repair (NER)
e. a and d only - CORRECT ANSWER e. a and d only
(Transcription-Coupled Repair and Nucleotide Excision Repair)
O6 - methylG may be generated by ______ and this modified base has a tendency to pair with T. Therefore if it is not repaired prior to replication its presence in DNA would lead to _________.
a. oxidation/transitions
b. deamination/transverions
c. alkylation/transitions
d. oxidation/deletions or insertions
e. alkylation/transversions - CORRECT ANSWER c. alkylation/transitions
What happens to the core DNA polymerase III (in E.coli) on the lagging strand template when it completes the synthesis of an Okazaki fragment?
a. It starts removal of the RNA primer and replaces it with DNA.
b. It disengages from the beta clamp
c. It begins proofreading the completed Okazaki fragment
d. It cycles to the helicase/SSB complex at the replication fork\
e. All of the above - CORRECT ANSWER b. It disengages from the beta clamp
In transcription-coupled repair (TCR), how is the presence of a lesion thought to be detected?
a. There are special enzymes that can scan the DNA for such lesions
b. The lesion is signaled by a stalled DNA polymerase
c. The lesion is signaled by a stalled RNA polymerase
d. The lesion is signaled by a stalled peptidyl transferase
e. The lesion is detected by single-stranded binding proteins - CORRECT ANSWER c. The lesion is signaled by a stalled RNA polymerase
Which of the following is false when activation of oriC and ARS are compared?
a. The initiator that binds to oriC is DnaA and the initiator that binds to ARS is a heterohexamer called ORC.
b. In both cases the initiators bind to the cis-acting elements within the origins in a sequence specific manner.
c. In both cases binding of the initiators to the origins is required for the recruitment of other proteins that are
necessary for the formation of replication forks
d. none of the above
e. both b and c are false - CORRECT ANSWER d. none of the above are false
Assuming there are 9 TCGA sequences within a 600 bp long regulatory region of an eukaryotic gene. How many of these tetramers would you expect to find in a 600 bp sequence anywhere else in the genome assuming that all 4 bases are present in equal proportions?
a. most likely none
b. maybe 2
c. probably 4
d. more than 5
e. can't predict - CORRECT ANSWER b. maybe 2
The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer. You add polynucleotide phosphorylase to a solution of adenosine triphosphate and guanosine triphosphate. The resulting artificial mRNA molecule would have ____ possible different codons if the code involved three-base sequences and ____ possible different codons if the code involved four-base sequences.
a. 16;32
b. 4;8
c. 4;16
d. 8;16
e. 16;64 - CORRECT ANSWER d. 8; 16
Statement A. The activation of origins of replication is very similar in all bacteria and requires sequence-specific binding of initiator proteins, melting of AT rich region by initiators, that is followed by recruitment of replication machinery.
Statement B. At all origins of replication helicases are loaded onto DNA by helicase loaders but only in bacteria they are loaded directly onto single stranded DNA that was melted by the initiators. - CORRECT ANSWER Both A and B are true
Statement A. In eukaryotes the pre-replicative complex (pre-RC) can be formed only during G1 but it remains inactive until the onset of S phase.
Statement B. The ability to form pre-RCs or to activate them during different stages of the cell cycle is controlled by the level of activity of Cdk (cyclin dependent kinase) - CORRECT ANSWER Both A and B are true
Transcription involves synthesis of an RNA chain representing one strand ofa DNA duplex. The strand with the complementary sequence to RNA product is the ________ strand and the one that has the "same" sequence as the RNA productis the ________ strand.
a. antisense/sense
b. noncoding/nontemplate
c. template/coding
d. all of the above
e. only b and c are correct - CORRECT ANSWER d. all of the above
What is the advantage of transcription-coupled repair?
a. It allows the cell to do two things at once.
b. It ensures that the genes of greatest importance to a particular cell receive the highest priority on the repair list.
c. It ensures that the genes with most extensive damage receive the highest priority on the repair list.
d. It repairs noncoding sequences preferentially.
e. It is the most accurate method of repair. - CORRECT ANSWER b. It ensures that the genes of the greatest importance to a particular cell receive the highest priority on the repair list
Which of the following is most likely to produce a frameshift mutation?
a. alkylaing agents
b. nitrous acid
c. UV radiation
d. intercalating agents
e. oxidation of a base - CORRECT ANSWER d. intercalating agents
In higher eukaryotes many of the Cs followed by Gs in the so called CpG islands are methylated resulting in 5-mC. These bases have a tendency to undergo _______ by water giving rise to Ts. If these Ts are not removed prior to replication by _________ they will cause __________.
a. alkylation/BER/transversions
b. deamination/NER/insertions
c. alkylation/ BER/transitions
d. deamination/BER/transitions
e. deamination/NER/transitions - CORRECT ANSWER d. deamination/BER/transitions
Which of the following is false about Ames test?
a. Mutagens at high concentrations may be cytotoxic and result in fewer colonies than on the control plates (no test
chemical present).
b. Chemicals that are genotoxic, at concentrations that are not cytotoxic, result in more colonies than on the control
plates.
c. Auxothrophic bacterial strains are used to look for revertants.
d. Chemicals that may be converted during the detoxification process to mutagens are treated 1st with liver extracts.
e. None of the above - CORRECT ANSWER e. None of the above are false; all are true of Ames Test
Here is a sketch of a replication bubble, as you might see in E. coli. Arrows inside the bubble indicate the direction of the replication forks.
If the arrow outside the bubble (red arrow) represents the 3' end of the strand it is nearest to, where is (are) the most likely place(s) to see the Okazaki fragments? - CORRECT ANSWER Positions closest to letters (c) and (a) [Show Less]