D2L Quizzes 10, 11, 12

Question 1

How can antiparallel DNA strands (5’ –> 3’ and the other is 3’ –> 5’) be synthesized in such a way that the replication fork moves in only one direction?

Answer 1

One of the strands is synthesized using Okazaki fragments

Question 2

Based on the cleavage below, cleavage at which two sites followed by DNA strand rejoining would lead to no change in the existing genetic information?
The holiday junction is red and green together and blue and orange together. each strand is then separated and just red is 2 (top), just orange is 4 (bottom), green meets blue is 1 (left), and green meets blue is 3 (right)

Answer 2

1 and 3
Because the DNA would cleave where the colors rejoin and remain the same

Question 3

If one parents has Lynch syndrome, but the other does not, what is the likelihood that the child will also have Lynch syndrome?

Answer 3

50%

Question 4

What is the function of the enzyme telomerase in eukaryotic DNA synthesis?

Answer 4

It synthesized DNA on the lagging strand at the ends of chromosomes

Question 5

Homologous recombination repairs…

Answer 5

double stranded breaks in DNA

Question 6

Match the name of the DNA repair mechanism with the correct description
1. Mismatch repair
2. Base-excision repair
3. Nucleotide-excision repair
4. Direct repair

• Repairs nucleotide bases without requiring DNA ligase.
• Is needed to repair chemical damage in DNA effecting more than one nucleotide, such as cyclobutane pyrimidine dimers
• Functions with DNA replication to remove incorrect nucleotides from the nascent strand
• Requires an endonuclease to remove an abasic nucleotide before DNA Pol 1 can replace a portion of the strand

Answer 6

Direct repair: Repairs nucleotide bases without requiring DNA ligase.

Nucleotide- excision repair: Is needed to repair chemical damage in DNA effecting more than one nucleotide, such as cyclobutane pyrimidine dimers

Mismatch repair: Functions with DNA replication to remove incorrect nucleotides from the nascent strand

-Base-excision repair: Requires an endonuclease to remove an abasic nucleotide before DNA Pol 1 can replace a portion of the strand

Question 7

The Tus-Ter complex terminates DNA synthesis in E. coli by…

a) breaking the single strand DNA and precenting further synthesis
b) blocking the opening of helicase
c) forcing the primase to dissociate
d) methylating the DNA strand

Answer 7

b) blocking the opening of helicase

Question 8

When a cytosine is deaminated to form uracil and removed by glycosylase enzymes, a _______ site is generated

a) deaminated
b) abasic
c) dibasic
d) nonbasic

Answer 8

b) abasic

Question 9

Which DNA repair mechanism is required to fix replication errors in E. coli?

a) mismatch repair
b)degrading of the entire DNA strand to start over
c) basic repair
d) base excision

Answer 9

a) mismatch repair

Question 10

A holliday junction can best be defined as a region of _________

A) DNA pyrimidine duplexes
b) DNA damage
c) duplex DNA
d) quadruplex DNA

Answer 10

d) quadruplex DNA

Question 11

RNA is more susceptible to backbone hydrolysis than DNA because of the…

a) presence of similar nucleotides
b) lack of thymine nucleotides
c) presence of a 3’ OH group
d) presence of a 2’ OH group

Answer 11

d) presence of a 2’ OH group

Question 12

Individuals with mutations of BRCA have increased incidence of cancer because of…

a) decreased ability to repair single-strand DNA breaks
b) decreased ability to repair double strand DNA breaks
c) increased ability to form pyrimidine dimers
d) increased ability to form methylated guanine

Answer 12

b) decreased ability to repair double-strand DNA breaks

Question 13

The function of the beta-clamp in DNA replication is to…

a) separate the DNA into a single strand
b) keep pol III complex associated with the DNA
c) add RNA primer
d) keep the torsional strain reduced

Answer 13

b) keep the Pol III complex associated with the DNA

Question 14

The ________ contains the enzymes and proteins required to replicate DNA

a) primase
b) DNA gyrase
c) replisome
d) polymerase

Answer 14

c) replisome

Question 15

Long noncoding RNA (IncRNA) is generated from…

a) the tips of chromosomes
b) an infection of viral RNA
c) the transcription of genomic DNA
d) the splicing of used mRNA

Answer 15

c) the transcription of genomic DNA

Question 16

What are the functions of the enzymes helicase and gyrase in DNA replication?

a) gyrase synthesizes RNA primers and helicase
b) helicase synthesized DNA and gyrase prevents helicase from dissociating
c) helicase unwinds DNA and gyrase relieves the torsional strain
d) gyrase adds the RNA primer and helicase removes it

Answer 16

c) helicase unwinds DNA and gyrase relieves the torsional strain

Question 17

The MutS-MutL-MutH protein complex is required for…

a) DNA adenylation
b) mismatch DNA repair
c) DNA methylation
d) base excision
e) resolution of Holliday junctions

Answer 17

b) mismatch DNA repair

Question 18

Excess exposure to ultraviolet light can cause DNA damage because it…

a) causes protein misfolding
b) causes an abasic site to form
c) causes double strand breaks in DNA
d) produces photoproducts
e) produces methylated thymidine

Answer 18

d) produces photoproducts

Question 19

AZT is useful in the treatment of AIDS-HIV because it…

a) allows DNA to repair itself after viral DNA is added
b) allows DNA to be replicated at a slower rate
c) prevents HIV from binding to the cell
d) prevents new DNA from being replicated

Answer 19

d) prevents new DNA from being replicated

Question 20

All DNA is synthesized in the ________ direction

a) 3’–> 5’
b) 5’ –> 1’
c) 1’ –> 5’
d) 5’–> 3’

Answer 20

d) 5’–> 3’

Question 21

Key components of the E.coli OriC region is…

a) the RNA primer
b) three 13-bp repeats and four 9-bp repeats with enriched G-C base pairs
c) three 13-dp repeats and four 9-bp repeats with enriched A-T pairs
d) 20 subunits of A-T pairs

Answer 21

c) three 13-dp repeats and four 9-bp repeats with enriched A-T pairs

Question 22

In the Nirenberg-Leder experiment, the _______ was radioactively-labeled

a) mRNA
b) aminoacyl-tRNA
c) ribosome
d) tRNA

Answer 22

b) aminoacyl-tRNA

Question 23

Place the following steps in the elongation phase of mRNA translation into the proper order:

A) Peptide bond formation occurs
B) GTP is hydrolyzed, and the ribosome moves one codon in the 3’ direction
C) GTP is hydrolyzed, and EF-Tu*GDP is released
D) tRNA is released from the E site

a) A C B D
b) C A B D
c) B D C A
d) A B C D

Answer 23

b) C A B D

Question 24

DNA footprinting technique is used to identify the…

a) DNA sequence
b) promotor region of a gene
c) location of a DNA binding protein on DNA
d) location of a gene in DNA

Answer 24

c) location of a DNA binding protein on DNA

Question 25

The ______ strand of DNA is transcribed into mRNA a) leading b) lagging c) coding d) template

Answer 25

d) template

Question 26

The spliceosome... a) resembles group II introns in its mechanism and product b) is a cis-acting ribozyme c) performs the same function in prokaryotes and eukaryotes d) is a protein enzyme

Answer 26

a) resembles group II introns in its mechanism and product

Question 27

Which of the following statements is correct regarding spliceosome-mediated trans splicing? a) the snRNPs involved in splicing are not recycled b) the spliceosome mechanism closely resembles the mechanism of group I introns c) the spliceosome mechanism involves two transesterification reactions d) the spliceosome is composed only of proteins

Answer 27

c) the spliceosome mechanism involves two transesterification reactions

Question 28

The initiation of transcription in eukaryotes... a) requires many more transcription factors than prokaryotic transcription b) uses RNA polymerase as well as helicase and primase c) requires the complete unfolding of the gene into single-stranded DNA d) occurs in the same manner as prokaryotic transcription

Answer 28

a) requires many more transcription factors than prokaryotic transcription

Question 29

RNA interference is mediated by __________ leading to mRNA degradation a) snoRNA b) miRNA c) rRNA d) siRNA

Answer 29

d) siRNA

Question 30

The main difference between group I and group II introns is... a) nucleophilic versus electrophilic hydroxyl attacks b) cis versus trans cleaving capabilities c) linear versus lariat intron products d) intron cleaving versus exon ligating abilities

Answer 30

c) linear versus lariat intron products

Question 31

A common RNA base modification is __________ a) amination b) carboxylation c) hydroxylation d) methylation

Answer 31

d) methylation

Question 32

Why does RNA contain uracil and DNA contain thymine? Choose the ONE best answer to this question a) Spontaneous cytosine deamination generates uracil, which base pairs with adenine during replication, and thereby converts a C-G base pair to a T-A base pair b) RNA transcription base pairs U-T in the RNA with DNA, whereas this process base pairs A-T in the RNA with DNA. Therefore, if uracil were present in DNA, then U-A and A-U could not be distinguished. c) Loss of NH3 from cytosine generates uracil, which base pairs with thymine and cause damage in DNA. If deamination of thymine generated guanine, then this would not be a problem. d) Uracil specifies RNA polymerization, and therefore, if uracil is inserted into DNA, then RNA polymerization will occur on DNA strands. e) DNA damage can alter the nucleotide bases and cause mutations that cannot be repaired if the base is uracil since repair enzymes recognize thymine in DNA, not uracil.

Answer 32

a) spontaneous cytosine deamination generates uracil, which base pairs with adenine during replication, and thereby converts C-G base pair to a T-A base pair

Question 33

The antibiotics streptomycin, tetracycline, and chloramphenicol all in interfere with... a) cell membrane formation b) nucleic acid synthesis c) cell wall formation d) protein synthesis

Answer 33

d) protein synthesis

Question 34

Both prokaryotes and eukaryotes recognize the mRNA sequence _______ as a translational start codon a) 5'-AUG-3' b) 5'-UAC-3' c) 5'-CAU-3' d) 5'-GUA-3'

Answer 34

a) 5'-AUG-3'

Question 35

The Shine-Dalgarno sequence of mRNA base pairs with the ____ rRNA within the prokaryote ____________ ribosomal subunit a) 16S; 30S b) 5S; 50S c) 23S; 30S d) 40S; 60S e) 16S; 50S

Answer 35

a) 16S; 30S

Question 36

Francis Crick hypothesized that the Genetic Code must require 3 nucleotides in the mRNA to specify each amino acid based on a simple calculation. What was the logic behind this calculation? Choose the ONE best answer. a) based on the number of known amino acids and the number of known tRNA molecules b) based on the number of known tRNA molecules and the number of known nucleotide bases c) based on the number of known amino acids and the number of known nucleotide bases d) based on the fact that the thymine is present in DNA but uracil is present in RNA,, each of the base pair with adenine e) 4 x 4 = 16, whereas 4 x 4 x 3 = 48, and since there are 20 amino acids, it must require 3 codons (48 > 16)

Answer 36

c) based on the number of known amino acids and the number of known nucleotide bases

Question 37

The bacterial sigma factor dissociate from the RNA polymerase __________ a) in the termination phase b) during the elongation phase c) in the initiation phase d) before the elongation phase

Answer 37

b) before the elongation phase

Question 38

Nirenberg and colleagues determined a portion of the genetic code using filter binding assays that included ribosomes, trinucleotides and tRNA molecules charged with radioactively-labeled amino acids. Choose the answer below that correctly answers the following three questions in order: 1) If the trinucleotide sequence is CAG, which amino acid will be bound to the filter paper? 2) if the wobble position of the trinucleotide sequence is changed to a U, which amino acid will be bound to the filter paper? 3)True or False: two distinct tRNA molecules with different anticodon sequences MUST be used to recognize the codons AGA and AGG a) 1) Asp 2) His 3) False b) 1) Asp 2) His 3) True c) 1) Val 2) Tyr 3) False d) 1) Gln 2) His 3) False

Answer 38

d) 1) Gln 2) His 3) False

Question 39

tRNA is _____ before binding to the ribosome to allow for translation to occur a) charged with an anticodon b) charged with a codon c) charged with an amino acid d) bound by ATP

Answer 39

c) charged with an amino acid

Question 40

Where do amino acids attach to tRNA?

Answer 40

At the 3' end of the tRNA, at the top left

Question 41

Based on the sequence of the double stranded DNA shown above, which sequence below corresponds to the mRNA transcript? Promoter: (5') CGCTATAGCGTTT (3') (3') GCGATATCGCAAA (5') Coding sequence a) 5'-CGCTATAGCGTTT-3' b) 5'-UUUGCGAUAUCGC-3' c) 5'-AAAGCGAUAUCGC-3' d) 3'-CGCUAUAGCGUUU-5' e) 5'-GCGAUAUCGCAAA-3' f) 5'-CGCUAUAGCGUUU-3' g) 5'-CGCUAUAGCGUUU-3' h) 5'-GCGUAUAGCGAAA-3'

Answer 41

g) 5'- CGCUAUAGCGAAA- 3'

Question 42

If tRNA are charged with radioactively- labeled amino acids in an vitro system, then over time the radioactivity will be located in newly synthesized... a) aminoacyl tRNA synthetase b) mRNA c) protein d) codons

Answer 42

c) proteins

Question 43

A lipid-modified protein is most likely localized to the... a) mitochondria b) plasma membrane c) proteasome d) nucleus

Answer 43

b) plasma membrane

Question 44

The control point for prokaryotic gene regulation primarily occurs at the point of... a) translational initiation b) genetic recombination c) mRNA processing d) transcriptional initiation

Answer 44

d) transcriptional initiation

Question 45

What are the functions of the HAT and HDAC enzymes with regard to regulating gene expression in eukaryotic cells? a) both HAT and HDAC activate the gene b) HAT activates the gene and HDAC represses the gene c) HAT represses the gene and HDAC activates the gene d) Both HAT and HDAC repress the gene

Answer 45

b) HAT activates the gene and HDAC represses the gene

Question 46

The function of CRP in lac operon expression is to _________ the promoter by causing RNA polymerase to ________ a) stimulate; dissociate b) inhibit; dissociate c) stimulate; bind tighter d) inhibit; bind tighter

Answer 46

c) stimulate; bind tighter

Question 47

Histone acetylation leads to ____________ with regard to transcriptional regulation a) RNA interference b) increased transcriptional activity c) repression of transcription d) repression of transcription

Answer 47

b) increased transcriptional activity

Question 48

One of the most common binding interactions between proteins and DNA are ______ bonds a) polar b) covalent c) hydrogen d) ionic

Answer 48

c) hydrogen

Question 49

Place the following steps in the correct order describing the steps required for synthesis of a membrane- bound protein A) GTP binds to SRP B) Protein synthesis occurs on free ribosome C) protein synthesis halts D) SRP binds to the signal peptide sequence a) D C B A b) A B D C c) A B C D d) B D C A

Answer 49

d) B D C A

Question 50

Assume that you have identified all the cis-acting sites in a prokaryotic genome for a particular trans-acting transcription factor. What is the function of this transcription factor when binding to these sites? a) it is most likely a ligand-dependent de-repressor since the lac repressor uses this mode of regulation b) it is most likely a ligand-dependent repressor since the trip repressor uses this mode of regulation c) assume that it is a repressor unless it requires cAMP and then it assume it is an activator like CRP-cAMP d) it is not possible to predict the function from the sites since could activate or repress at different sites e) if the site has the sequence GATC-CTAG then it is an activator, if GATC-GATC then it is a repressor

Answer 50

d) it is not possible to predict the function from the sites since could activate or repress at different sites

Question 51

The function of the lac operon is to provide... a) the enzymes needed to produce lactose b) beta-lactamase to inhibit penicillin c) the ability to distinguish glucose from galactose d) the enzymes needed to utilize the disaccharide lactose

Answer 51

d) the enzymes needed to utilize the disaccharide lactose

Question 52

When the Trp repressor is bound to the trp operon, it results in the ______ by RNA polymerase a) initiation b) disruption of transcriptional elongation c) enhancement of transcriptional elongation d) inhibition of transcriptional initiation

Answer 52

d) inhibition of transcriptional initiation

Question 53

The primary function of the transcriptional activator proteins is to... a) initiate DNA synthesis b) recruit gene promotors to the regulatory site c) recruit other transcription factors to the gene promoter d) initiation RNA synthesis

Answer 53

c) recruit other transcription factors to the gene promoter

Question 54

If a protein is covalently modified by ubiquitin, it will be... a) secreted by the proteasome b) anchored to the plasma membrane c) degraded by the proteasome d) degraded by lysosomes

Answer 54

c) degraded by the proteasome

Question 55

Together, the eight histone molecules are called the histone... a) octane b) tetramer c) octamer d) dimer

Answer 55

c) octamer

Question 56

When there is no lactose in a cell, transcription of the lac operon... a) is stimulated b) is activated but only when glucose levels are high c) is inhibited d) production of lac operon doe snot depend on lactose concentration

Answer 56

c) is inhibited

Question 57

When the trp operon is attenuated, then _____ occurs a) initiation by RNA polymerase b) inhibition of transcriptional inhiation by RNA polymerase c) enhancement of transcriptional elongation by RNA polymerase d) disruption of transcriptional elongation by RNA polymerase

Answer 57

d) disruption of transcriptional elongation by RNA polymerase

Question 58

What are the two main types of stem cells? a) stromal and embryonic b) stromal and somatic c) somatic and embryonic d) somatic and epithelial f) genetic and epigenetic

Answer 58

c) somatic and embryonic

Question 59

The best description of how allosteric regulation works is that a ligand __________ the transcriptional regulatory protein, which __________ the protein’s affinity for DNA. a) covalently modifies: increases b) binds to: causes conformational changes that affect c) binds to; causes conformational changes that can only decrease d) covalently modifies; decreases

Answer 59

b) binds to: causes conformational changes that affect

Question 60

The figure below shows ____ autoregulation and that _____ figure: promoter that has a negative sign with a repressor protein graph: starts everywhere then all lines even out a) positive: will no be expressed in the absence of an activator b) negative; reaches a steady state of expression c) positive reaches a steady state of expression d) negative; will not be expressed in the absence of an activator

Answer 60

b) negative; reaches a steady state of expression

Question 61

The _____ requires hydrolysis of GTP as a key step in the insertion of a newly synthesized protein into the ER lumen a) binding of SRP to the signal peptide sequence b) binding of SRP to the SRP receptor c) release of SRP from the ribosome d) transfer of the signal peptide sequence into the translocon

Answer 61

d) transfer of the signal peptide sequence into the translocon

Question 62

When tryptophan levels inside a bacterial cell are elevated then... a) there is initiation of RNA polymerase b) Trp repressor is not bound to DNA c) Trp repressor is bound to DNA d) transcriptional elongation by RNA polymerase is enhanced

Answer 62

c) Trp repressor is bound to DNA

Question 63

iPS cells can be defined as ____cells a) differentiated b) somatic stem c) dedifferentiated d) embryonic stem

Answer 63

c) dedifferentiated