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All EXCEPT which of the following are characteristics of the genetic material?

It must be replicated accurately.
It is composed of protein.
It must be capable of change.
It contains all the information needed for growth, development, and reproduction of the organism.

It is composed of protein.

What observation did Griffith make in his experiments with Streptococcus pneumoniae?
The mouse did not survive when injected with a mixture of live, avirulent (rough) Streptococcus pneumoniae and heat-killed, virulent Streptococcus pneumoniae.
The heat-killed, virulent Streptococcus pneumoniae was lethal to the mouse.
The mouse survived injection of live virulent (smooth) Streptococcus pneumoniae.
That DNA is the genetic material.

The mouse did not survive when injected with a mixture of live, avirulent (rough) Streptococcus pneumoniae and heat-killed, virulent Streptococcus pneumoniae.

What results did Avery, McLeod, and McCarty obtain in their experiments with virulent bacteria?
DNase destroyed the transforming activity.
RNase destroyed the transforming activity.
Protease destroyed the transforming activity.
The transforming principle was too complex and difficult to be purified.

DNase destroyed the transforming activity.

Why did Hershey and Chase use the isotopes 32P and 35S in their experiments?
32P labeled DNA only; 35S labeled protein only
35S labeled lipids only; 32P labeled DNA only
35S labeled DNA only; 32P labeled protein only
32P labeled DNA only; 35S labeled carbohydrates only

32P labeled DNA only; 35S labeled protein only

All EXCEPT which of the following statements are evidence that DNA, and not protein, is the genetic material in eukaryotes as well as bacteria?
UV light is most mutagenic at a wavelength at which DNA and RNA strongly absorb.
DNA has four nucleotides.
Introduction of a cloned DNA into another organism results in the production of the corresponding protein product.
DNA is located only where the primary genetic function is known to occur.

DNA has four nucleotides.

Which enzyme makes DNA from an RNA template?
Reverse transcriptase
DNA polymerase
Replicase
RNA polymerase

Reverse transcriptase

Watson and Crick used information from several individuals to construct their model of DNA. Whose X-ray diffraction studies were critical to their work?
Phoebus Levene
Rosalind Franklin
Erwin Chargaff
Linus Pauling

Rosalind Franklin

Which of the following statements about DNA structure is true?
The nucleic acid strands in a DNA molecule are oriented antiparallel to each other, meaning they run in opposite directions.
The pentose sugar in DNA is ribose.
Nucleic acids are formed through phosphodiester bonds that link nucleosides together.
Z-DNA is the most common form in living cells.

The nucleic acid strands in a DNA molecule are oriented antiparallel to each other, meaning they run in opposite directions.

RNA differs from DNA in all EXCEPT which of the following ways?
the number of different functions performed
the sugar molecule
the presence of uracil
the 5'-3' orientation of the polynucleotide strand

the 5'-3' orientation of the polynucleotide strand

Which technique can be used to identify the location of genes on a chromosome?
electrophoresis
FISH
reassociation kinetics
X-ray diffraction analysis

FISH

In the Meselson-Stahl experiment, which mode of replication was eliminated based on data derived after one generation of replication?
dispersive
conservative
semiconservative
none of the modes

conservative

Which DNA polymerase is mainly responsible for genome replication in E. coli?
DNA polymerase III
DNA polymerase \alpha
DNA polymerase II
DNA polymerase I

DNA polymerase III

Which enzyme in E. coli is responsible for relieving the tension ahead of the fork that results when the DNA unwinds to form the replication "bubble" or "eye"?
DNA gyrase
helicase
DNase
replicase

DNA gyrase

Which of the following statements is true regarding Okazaki fragments?
They are short fragments of RNA on the leading strand.
They are short fragments of DNA synthesized from RNA primers on the lagging strand.
They add nucleotides to the elongating DNA.
They are synthesized by ligase.

They are short fragments of DNA synthesized from RNA primers on the lagging strand.

Which activity of E. coli DNA polymerase I is responsible for proofreading the newly synthesized DNA?
3' to 5'; exonuclease
5' to 3' polymerase
3' to 5' endonuclease
5' to 3' exonuclease

3' to 5'; exonuclease

Which of the following statements about DNA replication is true?
The two replication forks move in the same direction.
DNA synthesis is discontinuous on the leading strand.
DNA synthesis is conservative on the leading strand and semiconservative on the lagging strand.
DNA synthesis is continuous on the leading strand and discontinuous on the lagging strand.

DNA synthesis is continuous on the leading strand and discontinuous on the lagging strand.

dnaG codes for ______.
DNA helicase
DNA polymerase I
Primase
DNA ligase

Primase

All EXCEPT which of the following are differences between eukaryotic and prokaryotic DNA replication?
the rate of DNA synthesis
the number of replication origins
the ability to form a replication fork
the type and number of polymerases involved in DNA synthesis

the ability to form a replication fork

All EXCEPT which of the following are related to telomeres?
telomerase enzyme
links to the aging process
found in eukaryotes and prokaryotes
short tandem repeats located at the ends of telomeres

found in eukaryotes and prokaryotes

Which term describes a genetic exchange between two DNA molecules with substantial DNA sequence homology?
site-specific recombination
somatic recombination
homologous recombination
illegitimate recombination

homologous recombination

What fluctuates in the fluctuation test of Luria and Delbruck?
The ratio of phages to bacteria (or multiplicity of infection) in the experiment
The probability of a bacterium coming in contact with a phage
The number of resistant cells in different aliquots from the same culture
The number of resistant cells from different independent cultures

The number of resistant cells from different independent cultures

Although the cultures were treated identically, random mutations gave random fluctuating numbers of resistant bacteria. The numbers fluctuated because the random mutations arose at different times in the different cultures and the resulting cells had varying amounts of time to grow and increase in number.

A point mutation occurs such that a codon is changed from AGA to AGC. Which term describes this mutation?
Insertion mutation
Transition mutation
Frameshift mutation
Transversion mutation

Transversion mutation

Transversions involve the substitution of a purine for a pyrimidine or vice versa. In this case, the substitution involved a change from the purine adenine to the pyrimidine cytosine.

Which of the following statements about deamination is true?
Deamination is induced by nitrous acid.
Deamination of cytosine gives thymine.
Deamination of cytosine causes a transversion mutation.
Deamination of thymine gives uracil.

Deamination is induced by nitrous acid.

All EXCEPT which of the following mutagenic events occur spontaneously?
Depurination
Tautomerization
Deamination
Alkylation

Alkylation

Myotonic dystrophy patients exhibit _______.
no dystrophin and a single nucleotide change
a triplet sequence repeated many times
no dystrophin
a single nucleotide change

a triplet sequence repeated many times

Myotonic dystrophy is characterized by several copies of the CTG repeat in a kinase gene.

Which of the following statements about mismatch repair is false?
It recognizes methylated cytosine.
It determines which base in a mismatch is the incorrect one.
It requires the action of a methylase.
It depends on the fact that parental strand DNA is more heavily methylated.

It recognizes methylated cytosine.

Mismatch repair recognizes methylated adenine at the sequence GATC, which contains all four bases and is a palindrome.

Which enzyme is responsible for proofreading during replication?
DNA glycosylase
RNA polymerase
DNA ligase
DNA polymerase

DNA polymerase

DNA polymerase performs proofreading functions during replication using its 3' to 5' exonuclease capability.

The Ames test is used to determine whether or not a compound causes _______.
DNA repair
gene mutations
chromosome mutations
Radiation mutagenesis

gene mutations

The Ames test assays various chemicals that may affect human health by causing mutations in genes.

All EXCEPT which of the following are good model organisms for genetic studies?
Drosophila melanogaster
Mus musculus
Humans
E. coli

humans

Transposons contain more genes than insertion sequences.
True
False

True

Transposons contain a transposase gene and other protein-coding genes unrelated to transposition. Insertion sequences do not contain these additional genes.

Both the codons UUU and UUC specify the amino acid phenylalanine. What is the term for this phenomenon?
Universal
Degenerate
Unambiguous
Non-overlapping

Degenerate

Which type of mutation helped lead to the understanding that the genetic code is based on triplets?
Base substitution (substitution of one base for another)
Nonsense
Frameshift
Missense mutation within the promoter

Frameshift

Insertions or deletions of one or two nucleotides resulted in frameshift mutations. Insertion or deletion of three nucleotides resulted in insertion or deletion of a single amino acid and did not shift the reading frame.

All EXCEPT which of the following experiments or discoveries helped to identify the "triplet nature" of the DNA code?
Anticodons
Repeating copolymers
Frameshift mutations
Universality of the genetic code

Universality of the genetic code

The universality of the code refers to the fact that, for the most part, all the DNA code of life's genomes can be read in the same way. In other words, a codon that represents leucine in bacteria, will also represent leucine in humans.

How many different codons code for amino acids?
20
61
3
64

61

There are 61 codons that code for amino acids and three stop codons that do not code for an amino acid.

The chromosome of phage φX174 encodes nine proteins consisting of a total of more than 2300 amino acids, even though the size of its genome predicts that it should be able to code for only 1795 amino acids. The reason for this discrepancy is
Alternative splicing
Frameshift mutations
Overlapping reading frames
Enhancers

Overlapping reading frames

Multiple translation initiation points allow a single mRNA to code for more than one protein.

The genetic code varies by organism and must be determined for each.
True
False

False

RNA synthesis from a DNA template is called _______.
transformation
transcription
transduction
translation

transcription

Transcription is initiated when the cell signals for the expression of a particular gene and involves the synthesis of RNA from a DNA template.

Which subunit of RNA polymerase establishes template binding to a promoter in prokaryotes?
Sigma
Beta prime
Alpha
Beta

Sigma

The sigma subunit recognizes the promoter sequence. Different sigma subunits can be employed to regulate the expression of genes at the transcriptional level.

What are two main types of posttranscriptional modifications that take place in the mRNA of eukaryotes?
The addition of a poly-T sequence at the 5' end of the gene and the addition of a poly-U tail at the 3' end.
The addition of a poly-A sequence at the 5' end and the addition of a 7-mG cap at the 3' end of the RNA transcript.
The addition of a 7-mG cap at the 5' end of the transcript and the addition of a poly-A sequence at the 3' end of the message.
The excision of the introns and the addition of a 7-mG cap to the 3' end.

The addition of a 7-mG cap at the 5' end of the transcript and the addition of a poly-A sequence at the 3' end of the message.

Most eukaryotic mRNAs are shorter than the genes that encode them. The reason for this is _______.
eukaryotic genes contain both introns and exons
addition of the poly-A tail to the genomic DNA
introns are spliced out of the DNA
exons are spliced out of the hnRNA

eukaryotic genes contain both introns and exons

After transcription, the introns are spliced out of hnRNA to form mRNA.

All EXCEPT which of the following are involved in the process of tRNA "charging?"
rRNA
ATP
Aminoacyl tRNA synthetase
Amino acids

rRNA

Ribosomal RNA and ribosomes form the site of protein translation. Transfer RNAs work to bring amino acids to the ribosome. After a tRNA contributes its amino acid to the growing polypeptide chain, it must be "recharged" with a new amino acid. This is done independently of rRNA.

Which of the following statements about translation is true?
The ribosome moves down the mRNA in the 5' to 3' direction and synthesizes protein in the direction of amino terminus to carboxyl terminus.
The ribosome moves down the mRNA in the 3' to 5' direction and synthesizes protein in the direction of carboxyl terminus to amino terminus.
The ribosome moves down the mRNA in the 3' to 5' direction and synthesizes protein in the direction of amino terminus to carboxyl terminus.
The ribosome moves down the mRNA in the 5' to 3' direction and synthesizes protein in the direction of carboxyl terminus to amino terminus.

The ribosome moves down the mRNA in the 5' to 3' direction and synthesizes protein in the direction of amino terminus to carboxyl terminus.

What event occurs during translocation?
The ribosome shifts in the 3' direction along the mRNA.
Amino acids are added to the polypeptide chain.
The two ribosomal subunits join to form a complex.
The polypeptide is cleaved from the terminal tRNA.

The ribosome shifts in the 3' direction along the mRNA.

Which of the following statements is true of translation in eukaryotes?
Ribosomes bind to the ribosome-binding sequence (RBS) near the 5' end of the mRNA.
Eukaryotes have coupled transcription and translation so the ribosome may bind the nascent mRNA as soon as the 5' end is made.
In eukaryotes, a given mRNA produces only one type of polypeptide chain.
All proteins start with the modified amino acid formyl methionine (fMet).

In eukaryotes, a given mRNA produces only one type of polypeptide chain.

Because the eukaryotic ribosome binds to the cap and not a ribosome-binding sequence, the ribosome cannot bind at any other site on the mRNA and begin translation at an internal site. Some viruses have evolved novel strategies to allow exception to this rule.

Which compound accumulates in the metabolic disorder alkaptonuria?
Homogentisic acid
Tyrosine
Phenylalanine
Phenylalanine hydroxylase

Homogentisic acid

Which of the following statements is true of a Neurospora valine auxotroph?
The cells can grow on minimal medium + valine.
The cells cannot grow on complete medium.
The cells can grow on minimal medium.
The cells can grow on minimal medium + histidine.

The cells can grow on minimal medium + valine.

Different sets of human hemoglobins are found at different times in development.
True
False

True

During embryonic and fetal development, the set of polypeptides found in hemoglobin is completely different from that found in the hemoglobin of adults.

Which level of protein structure do beta-pleated sheets and alpha helices represent?
Quaternary
Secondary
Tertiary
Primary

Secondary

The alpha helix and the beta-pleated sheet are examples of secondary structures that are formed as a result of the polypeptide chain folding back on itself, generated by interactions of H-bonds between nearby amino acids.

All except which of the following may occur during post-translational modification of a protein?
Removal of N-terminal amino acid
Addition of metals to create tertiary or quaternary structures
Removal of introns
Addition of phosphate groups

Removal of introns

Introns are removed from the mRNA posttranscriptionally in eukaryotes.

All except which of the following statements may apply to a protein domain?
Within a single protein, different domains may serve different functions, such as ligand-binding or catalysis.
Domains may have resulted from exons of different genes, which were reshuffled during evolution.
A domain consists of a single type of secondary structure.
Each protein contains at least one domain, but may contain several domains.

A domain consists of a single type of secondary structure.

A domain may contain more than one type of secondary structure.

Which term is used to describe enzymes that are produced only when specific substrates are present in the environment?
constitutive
inducible
repressible
negatively controlled

inducible

This term best describes enzymes that are produced only when specific substrates are present in the environment to induce their production.

What is the role of the lacZ gene product, the enzyme ß-galactosidase?
It facilitates the entry of lactose into the bacterial cell.
It converts lactose to glucose and galactose.
It converts simple sugars to lactose.
It removes the toxic by-products of lactose digestion from the bacterial cell.

It converts lactose to glucose and galactose.

It is essential that this conversion occur if lactose is to be used as an energy source, since glucose enters intermediary metabolism and glycolysis to provide the cell with carbon and energy.

What is the effect on transcription of the structural and regulatory genes of the lac operon when lactose is present in the environment?
Transcription of the structural genes occurs.
Lactose represses the synthesis of the repressor.
Transcription does not occur.
The genes are transcribed for only a single generation and then are shut off.

Transcription of the structural genes occurs.

Lactose changes the structure of the repressor such that it is unable to bind to the operator site, which in turn allows RNA polymerase to transcribe the structural genes.

Which of the following is an example of positive control in operons?
regulation of the lac operon by the lac repressor
attenuation of the trp operon
the regulation of the tryptophan operon by the trp repressor
the action of the catabolite activator protein (CAP) in the lac operon

the action of the catabolite activator protein (CAP) in the lac operon


CAP binds to its binding site in the lac operon and stimulates transcription.

What is the role of glucose in catabolite repression?
It represses transcription from the lac operon, causing a decrease in cAMP levels in the cell.
It stimulates transcription from the lac operon, causing an increase in cAMP levels in the cell.
It increases the levels of cAMP in the cell, stimulating transcription from the lac operon.
It decreases the levels of cAMP in the cell, repressing transcription from the lac operon.

It decreases the levels of cAMP in the cell, repressing transcription from the lac operon.


Glucose decreases the levels of cAMP in the cell, preventing formation of the CAP-cAMP complexes necessary for the stimulation of transcription from the lac operon.

Which of the following statements best describes the trp operon?
It is repressible and under negative control.
It is inducible and under positive control.
It is repressible and under positive control.
It is inducible and under negative control.

It is repressible and under negative control.

The trp operon controls the transcription of genes necessary for the synthesis of tryptophan. If tryptophan is present, these gene products are not needed and are therefore not synthesized. The trp operon is repressible, meaning that transcription occurs only when its substrate is absent. The gene will be transcribed unless it is shut down (negative control) by the presence of tryptophan.

What is the function of the hairpin loop in the mRNA transcript produced by the trp operon?
The hairpin loop is the binding site for the trp repressor.
The hairpin causes transcription to stop.
The hairpin loop brings tryptophan into the cell.
The hairpin loop is the corepressor.

The hairpin causes transcription to stop.

When the leader peptide sequence is transcribed, it gives rise to an RNA structure that folds back on itself and forms a hairpin loop. The loop is a terminator that causes RNA polymerase to cease transcription, dissociate from the DNA, and release the truncated mRNA.

Which of the following statements about the mechanism of attenuation is true?
When tryptophan levels are low, transcription of the leader sequence proceeds, but mRNA synthesis is terminated approximately 140 nucleotides along the transcript.
The levels of tryptophan in the environment affect only repression of the trp operon and do not affect attenuation.
When tryptophan is present at high concentrations, the repressor binds to the operator and transcription is initiated and not terminated. As a result, the enzymes required for the biosynthesis of tryptophan are translated.
When tryptophan levels are low, transcription is initiated and continues through the leader region into the structural genes, resulting in the production of a polycistronic mRNA and, ultimately, the enzymes required for the biosynthesis of tryptophan.

When tryptophan levels are low, transcription is initiated and continues through the leader region into the structural genes, resulting in the production of a polycistronic mRNA and, ultimately, the enzymes required for the biosynthesis of tryptophan.

What is a riboswitch?
a regulatory protein that binds to the promoter
a form of gene regulation based on alternative forms of RNA
inhibition of transcription based upon binding of a regulatory protein to the promoter
promotion of transcription based upon binding of a regulatory protein to the promoter

a form of gene regulation based on alternative forms of RNA

These RNAs assume different conformations depending upon binding of a ligand, such as amino acids, purines, vitamin cofactors, and metal ions. Some conformations promote transcription while others inhibit transcription.

Which feature of the arabinose operon is particularly unusual?
The product of the araC gene binds to the attenuator.
The regulatory protein is a simple negative regulatory protein.
The O2 region is the site at which ribosomes bind to block transcription.
It is an inducible operon in which the same regulatory protein can exert both positive and negative control.

It is an inducible operon in which the same regulatory protein can exert both positive and negative control.

The same protein acts to either induce or repress the operon, depending on conditions within the cell.

polA

DNA polymerase I

polB

DNA polymerase II

dnaE, N, Q, X, Z

DNA polymerase III subunits

dnaG

primase

dnaA, I, P

Initiation

dnaB, C

helicase at oriC

gyrA, B

gyrase subunits

lig

DNA ligase

rep

DNA helicase

ssb

single-stranded binding proteins

rpoB

RNA polymerase subunit

lacZ

codes for beta-galactoside, converts lactose to glucose and galactose

lacA

codes for transacetylase, not sure what it does, may be the removal of toxic by-products

lacY

codes for permease, facilitates entry of lactose into cells

positive control

transcription only occurs if a regulatory molecule directly stimulates RNA production

negative control

genetic expression occurs unless it is shut off by some type of regulator molecule

coding strand

same sequence as mRNA, except T is replaced with U

Template strand

always the one with the 3' OH end toward the promoter

Alanine

ala, nonpolar, hydrophobic

valine

val, nonpolar, hydrophobic

leucine

leu, nonpolar hydrophobic

isoleucine

ile, nonpolar, hydrophobic

proline

pro, nonpolar, hydrophobic

methionine

met, nonpolar hydrophobic

phenylalanine

phe, nonpolar, hydrophobic

tryptophan

trp, nonpolar, hydrophobic

glycine

gly, polar, hydrophilic

serine

ser, polar, hydrophilic

threonine

thr, polar, hydrophilic

cysteine

cys, polar, hydrophilic

tyrosine

tyr, polar, hydrophilic

asparagine

asn, polar, hydrophilic

glutamine

gln, polar, hydrophilic

lysine

lys, polar, positively charged, basic

arginine

arg, polar, positively charged, basic

histidine

his, polar, positively charged, basic

aspartic acid

asp, polar, negatively charged, acidic

glutamic acid

glu, polar, negatively charged, acidic

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