Exam #3 Flashcards
____ molecules deliver amino acids to ribosomes during translation.
tRNA
The strand of DNA for a particular gene that is copied by the RNA polymerase to form mRNA is called the ________ strand.
leading
template
transcription
copy
Template Strand
Each chromosome has one or more _________ site(s) where replication begins.
Origin
During replication, which enzyme unwinds the two strands of the DNA molecule from one another?
Ligases
Unwindases
Helicases
Primases
Helicases
The basic differences between RNA and DNA reside in their sugar and pyrimidine bases; RNA has ribose and uracil whereas DNA has deoxyribose and thymine.
True or False
TRUE
In the Hershey and Chase experiment, how did labeling DNA and protein with different radioactive isotopes demonstrate that DNA, rather than protein, carried the genetic information in the T2 virus?
Researchers could track which part of the virus entered a bacterial cell.
Researchers could use radio labeling to inactivate DNA and protein in the bacteria.
Researchers could distinguish bacterial DNA from viral protein.
Researchers could better elucidate DNA or protein structure.
Researchers could monitor how DNA interacted with protein in the virus
Researchers could track which part of the virus entered a bacterial cell.
Which of the following were used by Avery and colleagues to determine the molecule required to transform bacterial cells?
Protease
RNase
DNase
All of the choices are correct.
All are correct
Who first demonstrated transformation using mice and two strains of Streptococcus pneumoniae?
Griffith
Hershey and Chase
Avery, McCarty, and MacLeod
Watson and Crick
Jacob and Mono
Griffith
You and a classmate are discussing early experiments in genetics, and you state that Avery, MacLeod, and McCarty provided the first evidence that DNA carries genetic information. Your classmate argues that Griffith was the first to demonstrate this. Which statement best defends your argument?
Although Griffith first demonstrated transformation, Avery, MacLeod, and McCarty provided evidence that DNA rather than protein or RNA was the transforming agent.
Avery, MacLeod, and McCarty worked with purified DNA extracts while Griffith worked with bacterial strains.
Enzymes were used in the experiments carried out by Avery, MacLeod, and McCarty while Griffith transformed cells chemically or by using heat.
Because Avery, MacLeod, and McCarty did their experiments after those done by Griffith, they had much more information regarding the structure and function of DNA.
DNA used by Avery, MacLeod and McCarty was extracted solely from transformed strains of pneumococci, while Griffith used native pneumococcal strains.
Although Griffith first demonstrated transformation, Avery, MacLeod, and McCarty provided evidence that DNA rather than protein or RNA was the transforming agent.
DNA polymerases require which elements to replicate DNA?
A template, a primer, a source of energy
Because peptidoglycan lies outside the plasma membrane, all steps in the complex synthesis process of this molecule takes place outside the cell.
True or false
False
In the biosynthesis of nucleotides, pyrimidines are assembled starting with ribose-5-phosphate while ribose-5-phosphate is added after synthesis of the nitrogenous base for purines.
True or false
False
The synthesis of glucose 6-phosphate from noncarbohydrate precursors is called _________
Gluconegenesis
____ is the carrier molecule required to transport peptidoglycan subunits to the location where they will be incorporated into the growing bacterial cell wall.
Bactoprenol
UDP glucose
Acyl carrier protein
Malonyl-CoA
Bactoprenol
Many microbes use pyruvate carboxylase or phosphoenolpyruvate carboxylase _________
to synthesize amino acids
to synthesize oxaloacetate
to synthesize acetyl-CoA
to synthesize glucose
to synthesize oxaloacetate
The reduction of atmospheric nitrogen to ammonia is called _________
ammonification
nitrification
denitrification
nitrogen fixation
nitrogen fixation
Phosphorous is usually assimilated by microorganisms as
Phosphate
The use of pyruvate carboxylase to convert pyruvate into oxaloacetate is a step unique to gluconeogenesis compared to the Embden-Meyerhof pathway.
True or false
True
To convert a nucleoside into a nucleotide, what moiety must be added?
One or more purine bases
One or more double bonds
One or more phosphate groups
One or more pyrimidine bases
One or more phosphate groups
Cells save energy and materials by using many of the same enzymes for both _________ and _________.
Anabolism and catabolism
Which is true regarding translation in bacteria?
Translation begins with formation of the 30S initiation complex.
Translation ends when the Shine-Dalgarno sequence is reached.
The 70S ribosome is composed of a 20S and 50S subunit.
All of the choices are correct.
Translation begins with formation of the 30S initiation complex.
In _________, ribosomes can attach to the mRNA and begin translation even though transcription has not been completed.
bacteria
eukaryotes
fungi
protozoa and some plants
Bacteria
The first amino acid in a bacterial protein is N-formylmethionine; the presence of the formyl group makes it the initiator amino acid.
True or False
true
Which of the following is the initiator codon?
AUG
UAA
UAG
UGA
AUG
What is the key factor determining whether or not attenuation will occur when transcription of the E. coli trp operon has been initiated?
Multiple Choice
The activity level of adenyl cyclase
The trp operon repressor
The level of tryptophan in the environment
The level of trp-tRNA that is charged with tryptophan
The level of trp-tRNA that is charged with tryptophan
When tryptophan levels in a cell are low, a cell will stall transcription but continue translation of the trp operon.
true or false
false
The binding of arabinose to the AraC protein allows it to form a loop in the DNA upstream of the ara operon promoter.
True or False
False
One way to regulate gene expression is through the production of different sigma factors. These cause RNA polymerase to bind to different sets of promoters, thereby altering the pattern of gene expression
True or false
True
he activity of adenyl cyclase is influenced by
the phosphotransferase system
the presence of lactose in the environment
homoserine lactones
None of the choices are correct.
the phosphotransferase system
Which of the following statements is true?
The -10 sequence is critical for transcriptional termination
If you deleted the -35 sequence in bacteria, this would affect the
initiation of transcription
The mRNA start codon is not translated into an amino acid during translation
The -10 sequence is dispensable for transcription initiation
If you deleted the -35 sequence in bacteria, this would affect the
initiation of transcription
Rho factor is required for transcriptional termination
true or false
false
Aminoacyl-tRNA synthetases
remove the final tRNA from the ribosome, ending translation.
catalyze the transpeptidation reaction.
transport tRNAs to the ribosome.
catalyze the addition of amino acids to the correct tRNA.
catalyze the addition of amino acids to the correct tRNA.
if GTP levels in the cell are low, translation can still begin as long as IF2 levels are high.
True or false
false
The primary function of Ef-Ts is to deliver charged tRNAs to the ribosome.
True or false
false
in the Sec-dependent secretion pathway ___________________
SecA protein acts as a translational repressor.
only folded proteins are translocated.
co-translational translocation requires the signal recognition particle.
post-translational translocation requires the signal recognition particle.
co-translational translocation requires the signal recognition particle.
A critical factor in the state of the ara operon is whether or not AraC is in the dimeric state.
True or false
true
When glucose is low, but lactose is high, the lac operon would exhibit ______________________.
cAMP/CAP is bound and lac repressor bound.
CAP not bound, lac repressor not bound
cAMP/CAP bound, repressor absent.
neither CAP nor repressor bound.
cAMP/CAP bound, repressor absent.
Bacteria can assess the levels of attractant in their environment by comparing extracellular methylation levels with intracellular attractant levels.
true or false
False
In the CRISPR/Cas system _________.
methylase enzymes add methyl groups to the viral nucleic acids, preventing transcription
bacteria integrate portions of the viral genome into their own so they have a molecular snapshot of their attacker to prevent future encounters
restriction endonucleases digest viral genomes once they enter the cell if the viral DNA is not methylated
methylated DNA sequences are hydrolyzed, effectively destroying the viral DNA
bacteria integrate portions of the viral genome into their own so they have a molecular snapshot of their attacker to prevent future encountersCorrect
The chromosomes of most bacteria are comprised of _________
Multiple Choice
double-stranded circular molecules
double-stranded linear molecules
single-stranded circular molecules
single-stranded linear molecules
double-stranded circular molecules
Each chromosome has one or more ________site(s) where replication begins.
promoter
replicon
originCorrect
bifurcate
origin
Correct
The unexpressed regions of split genes are called _________
introns
Eukaryotic mRNAs are modified by the addition of a poly(A) sequence at the 3’ end and 7-methyl guanosine at the 5’ end.
T O F
true
RNA polymerase III of eukaryotes is responsible for transcribing _________
t RNA
RNA polymerase II of eukaryotes is responsible for transcribing _________
mRNA
in eukaryotes a series of _________ residues are added to the 3’ end of an RNA molecule as part of the posttranscriptional processing used to produce functional mRNA.
Multiple Choice
adenine
guanine
cytosine
uracil
adenine
Correct
Which of the statements best describes the function of telomerase?
Telomerase stabilizes the RNA polymerase during bacterial protein transcription.
Telomerase binds to specific DNA sequences that are not to be replicated and blocks polymerases.
Telomerase uses internal RNA as a template for lengthening the DNA single strand and preventing information loss.
Telomerase is responsible for forming the Okazaki fragments that allow for noncontinuous replication.
Telomerase uses internal RNA as a template for lengthening the DNA single strand and preventing information loss.
Homologues of the Sec protein translocation system are found in bacteria, eukaryotes, and archaea.
t o f
true
DNA is wound around which of the following to form nucleosomes?
histones
Microbial strains that can grow on minimal medium are called _________
Prototrophs
To best isolate mutant bacteria that are threonine auxotrophs from a larger population, threonine-rich media should be inoculated and any colonies that form are presumptive auxotrophic mutants.
T o F
false
Which type of medium support growth of mutant bacteria that are threonine auxotrophs?
Threonine auxotrophs only grow on media that is supplemented with threonine.
Threonine auxotrophs only grow on media that lacks threonine.
Since threonine is essential for growth, threonine auxotrophs do not grow on any type of media.
Since threonine is essential for growth, threonine auxotrophs can grow on any type of media.
Threonine auxotrophs only grow on media that is supplemented with threonine.
Correct
_________are strains that are unable to grow on a minimal medium that supports growth of the wild type strain, but are able to grow on the minimal medium if one or more nutritional supplements are added.
Autotrophs
Auxotrophs
Prototrophs
Minitrophs
Auxotrophs
Correct
A change in genotype, but not in phenotype, is most likely due to _________.
Multiple Choice
a nonsense mutation at the beginning of a gene
a point mutation in the third position of a DNA triplet
a mutation that leads to a frameshift in the middle of a gene
thymine dimer formation in the coding region of a gene
a point mutation in the third position of a DNA triplet
A _________ mutation does not alter the amino acid sequence of the resulting protein.
missense
nonsense
silent
silent
A mutation that changes the amino acid sequence of the resulting protein by substitution is called a _________ mutation.
missense
A _________ mutation is one that causes premature termination of the synthesis of the protein product.
nonsense
_________ mutations affect only a single base pair in a gene.
point
