Final Exam problems Flashcards
Predict how a lacI S mutant would be affected by the construction of a merodiploid that has a second normal copy of the lacI gene.
a) the lac genes would be expressed efficiently only in the absence of lactose
b) the lac genes would be expressed efficiently only in the presence of lactose
c) the lac genes would be expressed continuously
d) the lac genes would never be expressed efficiently
d) the lac genes would never be expressed efficiently
_______ opens strand and acts as guide for primase on both strands
Helicase
In specialized transduction
a) requires a phage that uses the lysogenic cycle for reproduction
b) only certain bacterial genes can be transferred and these genes, as you will see, must exist on either side of the prophage
c) a phage that uses the lytic cycle for reproduction
d) whatever piece of bacterial DNA happens to get packaged within the phage is the genetic material that will be transferred between cells.
e) A and B
e) A and B
A point mutation that changes a codon specifying an amino acid into a stop codon is called a a) missense mutation b) nonsense mutation c) frameshift mutation d) deletion mutation
b) nonsense mutation
(True/False) Some Hsp are chaperones that direct the folding of newly-translated proteins. In heat shock, they bind to denatured proteins and either help to refold them into their inactive conformations or, if the protein is extensively denatured, chaperones target these proteins for destruction.
False
The 70S ribosome moves a distance of one codon down the mRNA through a process called
a) site A or acceptor or aminoacyle site
b) translocation
c) peptidyl transferase
d) site P or peptide site
e) release factors
b) translocation
What is the consequence of a nonsense mutation?
a) Prevents DNA replication
b) Codes for the wrong amino acid
c) Deletes promoter region
d) Introduces a stop codon
d) Introduces a stop codon
Suppose there is not preference codon
The trp operon consists of ______ structural genes.
a) one
b) two
c) three
d) four
e) five
e) five
In the absence of tryptophan, the trp repressor is
a) active and can bind to the operator
b) active and cannot bind to the operator
c) inactive and cannot bind to the promoter
d) inactive and can bind to the operator
e) inactive and cannot bind to the operator
e) inactive and cannot bind to the operator
a) transformation
b) transduction
c) sexduction
d) conjugation
e) transposition
d) conjugation
(True/False) Sec YEG: proteins that assist the non-covalent folding/unfolding
True
(True/False) Gram-negative: have double cell membrane
True
One of the largest global regulatory systems in bacteria are
a) Catabolite-Sensitive operons
b) oxygen stress operons
c) pH shock system
a) catabolite-sensitive operons
Predict the phenotype of a promoter mutant (lacP) which has a mutation in the promoter for the lac operon.
a) the lac genes would be expressed efficiently only in the absence of lactose
b) the lac genes would be expressed efficiently only in the presence of lactose
c) the lac genes would be expressed continuously
d) the lac genes would never be expressed efficiently
d) the lac genes would never be expressed efficiently
Is where the growing amino acid chain is temporarily being held by a tRNA as the next codon in the mRNA is being read.
a) site A or acceptor or aminoacyle site
b) translocation
c) peptidyl transferase
d) site P or peptide site
e) release factors
d) site P or peptide site
A nucleic acid was analyzed and found to contain 32 perecnt A, 18 percent G, 17 percent C, and 33 percent T. The nucleic acid must be:
a) single-stranded RNA
b) single-stranded DNA
c) double-stranded RNA
d) double-stranded DNA
b) single-stranded DNA
DNA transformation involves the transfer of DNA via
a) pili
b) naked DNA in solution
c) a restriction endonuclease
d) a bacteriophage
b) naked DNA in solution
Go over on paper
A ______ mutation affects the phenotype only under certain conditions. a) spontaneous b) somatic c) site-directed d) conditional
d) conditional
(True/False) In transformation, both strands of donor DNA enter the recipient cell.
False
The lac operon is expressed when
a) glucose is high and lactose is present
b) glucose is high and lactose is absent
c) glucose is low and lactose is present
d) glucose is low and lactose is absent
e) glucose is low, regardless of the presence or absence of lactose
d) glucose is low and lactose is absent
(True/False) An operon is a group of genes that is under the control of a single operator site
False
_______ keep strand apart during the replication process
single-binding proteins
______ protein may be a “cellular thermometer” that senses the change in temperature and induces the transcription of heat shock genes
a) sigma 32
b) sigma E
c) DnaK
d) DnaI
c) DnaK
Below is the schematic representation of _________.
RNA polymerase
Replication continues until the replication fork enters a region of the chromosome called _______.
Ter
Indicate the function of sub-units
(True/False) Donor DNA is combined with recipient DNA by homologous recombination
True
Predict the phenotype of an operator mutant (Oc) which would prevent the binding of the repressor.
a) the lac genes would be expressed efficiently only in the absence of lactose
b) the lac genes would be expressed efficiently only in the presence of lactose
c) the lac genes would be expressed continuously
d) the lac genes would never be expressed efficiently
c) the lac genes would be expressed continuously
(True/False) Partitioning of the chromosome: is the distribution of one daughter chromosome to each of the two daughter cells.
True
Suppose the preference codon for S is 60% TCT, 30% TCC, and 2.5% in each of the other codons.
_______ extends strands only in 5’-3’ direction, thus one strand is continuous and one is in short fragments (Okazaki fragments)
DNA polymerase III
Changing the codon AGC to AGA represents a _______ mutation. a) missense b) nonsense c) frameshift d) deletion
b) nonsense
________ synthesize primer sequences that are used by DNA polymerase III
Primase
Predict the phenotype of the lacZ mutant, which has a mutation in the gene for Beta-galactosidase
a) the production of all protein products would be affected
b) the production of Beta-galactosidase would be affected, but other protein products woud be unaffected
c) the production of Beta-galactosidase would be affected, and the production of some other protein products might also be affected
b) the production of Beta-galactosidase woud be affected, but other protein products would be unaffected
__________ relaxes strands
Topoisomerase or Girase
Go over on paper
In the presence of tryptophan, tryptophan bind to the
a) operator
b) promoter
c) RNA polymerase
d) trp genes
e) trp repressor
e) trp repressor
(True/False) DNA synthesis on the lagging strand is continous
False
_______ is synthesized complementary to a gene and subsequently translated into a polypeptide or protein at ribosomes.
mRNA
Which mRNA codes for the following polypeptide?
MET ARG SER LEU GLU
a) 3’ aug cgu agc uug gag uga 5’
b) 3’ agu gag guu cga ugc gua 5’
c) 5’ aug cgu agc uug gag ugg 3’
d) 1’ aug cgu agc uug gag uga 3’
e) 3’ aug cgu agc uug gag uga 1’
c) 5’ aug cgu agc uug gag ugg 3’
Attenuation of the trp operon:
a) occurs when transcription is complete before translation begins
b) is mediated by the trp repressor protein
c) occurs in the presence of high levels of tryptophan
d) all of the above
e) none of the above
c) occurs in the presence of high levels of tryptophan
How would you descibe the regulation of lactose metabolism in the cells descibed in problem 11 that were able to grow on minimal media with lactose as a nutrient?
a) normal regulation of lactose metabolism
b) constitutive expression of lac Z+
c) inability to synthesize the lac Z+ gene product, Beta-galactosidase
d) lac Z+ gene is inducible, but unable to be repressed by high glucose
e) no synthesis of the lac I gene product, the lac repressor
a) normal regulation of lactose metabolism
(True/False) Promoter is a nucleotide sequence up stream of the gene to which RNA polymerase binds at the initiation of transcription.
True
Break the convalent bond that holds the finished protein to the terminal tRNA
a) site A or acceptor or aminoacyle site
b) translocation
c) peptidyl transferase
d) site P or peptide site
e) release factors
e) release factors
(True/False) In the lagging during the DNA synthesis, the Okasaki fragments are synthesized
True
Predict the phenotype of a lacI S or “super-repressor” mutant. A lacI S mutant synthesizes a repressor that cannot bind to the inducer
a) the lac genes would be expressed efficiently only in the absence of lactose
b) the lac genes would be expressed efficiently only in the presence of lactose
c) the lac genes would be expressed contnuously
d) the lac genes would never be expressed efficiently
d) the lac genes would never be expressed efficiently
(True/False) The replication of the bacterial chromosome is unidirectional
False
(True/False) In the presence of tryptophan, transcription of the trp operon is on
False
A bacterial cell that is able to take up naked DNA is said to be
a) competent
b) liable
c) infected
a) competent
Gene A contains a frameshift mutation. To revert that mutation (change it back to normal or wild type) you would use a
c) Mutagen causing frameshifts
The enzyme that creates a short RNA oligonucleotide at initiation sites where replication is to be carried out is called a) Primase b) DNA ligase c) DNA gyrase d) Exonuclease
a) Primase
A spontaneous mutation usually originates as an error in a) DNA replication b) DNA transcription c) translation d) reverse transcription
a) DNA replication
a) normal regulation of lactose metabolism
b) constitutive expression of lac Z+
c) inability to synthesize the lac Z+ gene product, Beta-galactosidase
d) lac Z+ gene is inducible, but unable to be repressed by high glucose
e) no synthesis of the lac I gene product, the lac repressor
b) constitutive expression of lac Z+
(True/False) When RNA polymerase is bound to the lac promoter sequence, transcription of the lac operon is on.
True
CAP contains an “activating region” that has been proposed to participate in direct protein-proteins interactions with RNA polymerase and/or other basal transcription factors.
a) in the Lac operon
b) in the Trp operon
c) in all catabolite-sensitive operons
d) in Ara operon
e) in Lac and Ara operons
c) in all catabolite-sensitive operons
When in a complex with ______, the CAP protein binds to the CAP site and ______ the expression of the lac operon
a) glucose; switches on
b) glucose; switches off
c) lactose; switches on
d) cAMP; switches on
e) cAMP; switches off
d) cAMP; switches on
A messenger is 336 nucleotides long, including the initiator and termination codons. The number of amino acids in the protein translated from this mRNA is: a) 999 b) 630 c) 330 d) 111 e) 110
d) 111
(True/False) Sigma 32 binds to the RBS of its own mRNA and blocks access of the ribosome
True
How many lac Z genes were present in the cells described in the previous problem (11) that were able to grow on minimal media?
a) Only 1, the lac Z- allele on the bacterial chromosome
b) Only 1, the lac Z+ allele on the bacterial chromosome
c) Two, the lac Z- allele on the bacterial chromosome and the lacZ+ allele on the bacterial chromosome.
d) Two, the lac Z- allele on the bacterial chromosome and the lac Z+ allel on the F’ episome
e) Only 1, the lac Z+ allele on the F’ episome
d) Two, the lac Z- allele on the bacterial chromosome and the lac Z+ allele on the F’ episome
Go over on paper
If a second wild type or normal copy of the lacI gene (just lacI and not lacZ, lacY, or lacA) is introduced into the lacI mutant cell, what would be the phenotype of this partial diploid ( also referred to as a merodiploid)?
a) the lac genes would be expressed efficiently only in the absence of lactose
b) the lac genes would be expressed efficiently only in the presence of lactose
c) the lac genes would be expressed continuously
d) the lac genes would never be expressed efficiently
b) the lac genes would be expressed efficiently only in the presence of lactose
(True/False) Bacteria have one circular chromosome, main genome ( which carries housekeeping genes)
True
______ RNA which is able to pick up a specific amino acid, transfers it to ribosomes.
tRNA
Predict the phenotype of the lacI mutant
a) the lac genes would be expressed efficiently only in the absence of lactose
b) the lac genes would be expressed efficiently only in the presence of lactose
c) the lac genes would be expressed continuously
d) the lac genes would never be expressed efficiently
c) the lac genes would be expressed continuously
To revert a transition mutation you would use a
a) Mutagen causing transitions
A mutation always causes a mutant phenotype. (True/False)
False
A prophage is
a) phage DNA integrated into host cell genome
b) phage DNA being actively expressed
c) phage protein left outside the bacterium
d) toxic to the host bacterial cell
a) phage DNA integrated into host cell genome
(True/False) Nucleotides in each strand are linked by 5’-3’ phosphodiester bonds
True
In the absence of lactose, the lac represor is
a) active and can bind to the operator
b) active and cannot bind to the operator
c) inactive and cannot bind to the promoter
d) inactive and can bind to the operator
e) inactive and cannot bind to the operator
a) active and can bind to the operator
To revert a transversion mutation, you would use a
b) Mutagen causing transversions
Transcriptional regulation during the development of a typical large DNA phage the _________ products are responsible for regulation the transcription (turn on or off the transcription of othe genes)
a) regulatory cascade
b) regulatory genes
c) lytic regulation
b) regulatory genes
Which of these descibes a similarity between the lac and ara operons?
a) expression of structural genes does ont occur at high glucose concentrations
b) lacI and araI both encode trans acting factors
c) binding of a regulatory protein is prevented in the presence of an inducer.
d) all of these are similarities
e) none of these are similarities
a) expression of structural genes does not occur at high glucose concentrations
Immediately after a temperature increase
a) most of the DnaK will have to help renature unfolded proteins, thus making DnaK unavailable for binding sigma 32. So free sigma 32 is more stable ( less susceptible to protease digestion) and more active
b) most of the DnaK will have to help renature unfolded proteins, thus making DnaK available for binding sigma 32. So free sigma 32 is less stable (less suceptible to protease digestion) and more active
c) most of the DnaK will be available for binding sigma 32; therefore bound sigma 32 is more stable (less susceptible to protease digestion) and more active
a) most of the DnaK will have to help renature unfolded proteins, thus making DnaK unavailable for binding sigma 32. So free sigma 32 is more stable ( less susceptible to protease digestion) and more active
Predict the phenotype of a lacY mutant, which has a mutation in the gene for lactose permease.
a) the lac genes would be expressed efficiently only in the absence of lactose
b) the lac genes would be expressed efficiently until the lactose supply in the cell is exhausted
c) the lac genes would be expressed continuously
d) expression of the lac genes would cease immediately
b) the lac genes woud be expressed efficiently until the lactose supply in the cell is exhaused
The peptide bond is formed by a ribozyme called
a) site A or acceptor or aminoacyle site
b) translocation
c) peptidyl transferase
d) site P or peptide site
e) release factors
c) peptidyl transferase
When DNA from an ampicillin resistant organism is brought into an ampicillin sensitive organism by transformation and the product is grown on agar containing ampicillin
a) only the transformed cells will grow
b) only donor cells will grow
c) all cells grow
d) no cells grow
e) only ampicillin sensitive cells grow
a) only the transformed cells will grow
( True/False) The inducer of the lac operon is an isomer of lactose
True
Is where an amioacyl-tRNA first attaches
a) site A or acceptor or aminoacyle site
b) translocation
c) peptidyl transferase
d) site P or peptide site
e) release factors
a) site A or acceptor or aminoacyl site
(True/False) The Ter region is the area that contains multiple symmetrically arranged sites for traping the replication fork.
True
