Exam #3 Flashcards by Emily Mendoza

____ molecules deliver amino acids to ribosomes during translation.

tRNA

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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

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Each chromosome has one or more _________ site(s) where replication begins.

Origin

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During replication, which enzyme unwinds the two strands of the DNA molecule from one another?

Ligases

Unwindases

Helicases

Primases

Helicases

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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

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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.

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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

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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

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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.

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DNA polymerases require which elements to replicate DNA?

A template, a primer, a source of energy

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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

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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

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The synthesis of glucose 6-phosphate from noncarbohydrate precursors is called _________

Gluconegenesis

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____ 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

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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

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The reduction of atmospheric nitrogen to ammonia is called _________

ammonification

nitrification

denitrification

nitrogen fixation

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Phosphorous is usually assimilated by microorganisms as

Phosphate

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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

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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

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Cells save energy and materials by using many of the same enzymes for both _________ and _________.

Anabolism and catabolism

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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.

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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

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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

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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