Mastering Chapter 8

Diphtheria toxin kills eukaryotic cells by affecting translation. More specifically, the toxin prevents movement of tRNAs from the A site to the P site of the ribosome. Predict what the result(s) of this inhibition would be.

-Protein synthesis will be interrupted because the peptide chain is inhibited from growing. -New tRNAs will not be able to enter the ribosome.

the stages in which the lagging strand is synthesized.

1. DNA polymerase begins synthesizing the lagging strand by adding nucleotides to a short segment of RNA. 2. After each piece of the lagging stand is complete, it is released from DNA polymerase. 3. A different DNA polymerase replaces the RNA segments with DNA. 4. DNA ligase seals the gaps between the pieces, and eventually forms continuous strand.

If the sequence of amino acids encoded by a strand of DNA is serine-alanine-lysine-leucine, what is the order of bases in the sense strand of DNA?

3' AGACGTTTCAAT

If the sequence of amino acids encoded by a strand of DNA is serine-alanine-lysine-leucine, the coding for the antisense strand of DNA is

5' TCTGCAAAGTTA.

During elongation, how is the RNA synthesized?

5' to 3'

Based on the animation, what is transferred during bacterial conjugation? A. RNA B. A bacterial chromosome C. A conjugation pilus D. A bacterial plasmid

A bacterial plasmid

Which of the following is NOT a product of transcription? a new strand of DNA rRNA tRNA mRNA None of the answers are correct; all of these are products of transcription.

A new strand of DNA

Generalized transduction

A phage infects the bacterial cell, thereby transferring bacterial, plasmid, and/or viral DNA to the recipient

Insertion sequences target which areas on a target DNA sequence?

A sequence of nucleotides identical to the inverted repeat sequence found on the insertion sequence itself

What would happen if the mRNA codon that coded for Cys was mutated in the third position from a U to an A?

A stop codon would be introduced prematurely.

Which of the following statements concerning transcription is true?

All types of RNA in the cell are synthesized by transcription, which uses a portion of DNA as a template for copying.

What is the inducer molecule in the lac operon?

Allolactose

Transformation is the transfer of DNA from a donor to a recipient cell

As naked DNA in solution.

Which of the following might result in a frameshift mutation? Nitrous acid Benzopyrene 5-bromouracil

Benzopyrene

Which type of transposon would contain a gene for transposes? Neither simple nor complex transposons; the transposase enzyme is coded independently by the cell. Complex transposons Simple transposons Both simple and complex transposons

Both simple and complex transposons

Codon on mRNA and corresponding amino acid UUA leucine UAA nonsense GCA alanine AAU asparagine AAG lysine UGC cysteine GUU valine UCG, UCU serine Refer to the table The anticodon for valine is

CAA

During infection, C. diphtheriae expresses a variety of genes that are used to establish infection and cause disease. One of these genes encodes for diphtheria toxin. Expression of the toxin requires the genetic information contained in DNA be converted into protein. The 1st step in this process is transcription, in which DNA is converted into mRNA. The following is a short piece of the DNA sequence for diphtheria toxin (written 5' to 3'): TAA GCG TAG AAC TTG. Which of the following sequences represents the mRNA (written 5' to 3') that will be generated from this template DNA sequence?

CAA GUU CUA CGC UUA

How do complex transposons differ from simple transposons? Complex transposons are found in multiple locations in the target DNA; simple transposons are found only in one location. Complex transposons code for additional genetic elements, such as antibiotic resistance genes; simple transposons only code for the transposes gene essential for the tranposon itself. Complex transposons code for transposase; simple transposons do not.

Complex transposons code for additional genetic elements, such as antibiotic resistance genes; simple transposons only code for the transposase gene essential for the tranposon itself.

Bacterial conjugation is often referred to as bacterial sex. Why is this term inaccurate? Bacteria are neither male nor female. Conjugation does not result in the formation of new offspring. It does not require two cells to occur. Sex is a phenomenon only seen in animals.

Conjugation does not result in the formation of new offspring.

Which statement about conjugation is false? A. Conjugation is a process of bacterial reproduction. B. E. coli is the model for bacterial conjugation. C. After conjugation, each cell involved has a copy of the shared DNA.

Conjugation is a process of bacterial reproduction.

What characteristic of DNA allows two connected DNA polymerases to synthesize both the leading and lagging strands?

DNA is flexible

The molecule that seals the gaps between the pieces of DNA in the lagging strand is the leading strand. RNA. the replication fork. DNA ligase. DNA polymerase.

DNA ligase

Which statement about DNA replication is FALSE? -the two strands of parental DNA are separated during DNA replication. -DNA ligase adds nucleotides to the lagging strand. -Because the two strands of parental DNA run in opposite directions, the new strands must be made in different ways. -The lagging strand is made of a series of pieces that must be joined together to make a continuous strand. -DNA polymerase builds a new strand by adding -DNA nucleotides one at a time.

DNA ligase adds nucleotides to the lagging strand.

Which of the following build(s) new strands of DNA? The leading strand The lagging strand DNA polymerases Parental DNA The origins of replication

DNA polymerases

Which of the following statements is FALSE? -The lagging strand of DNA is started by an RNA primer. -Multiple replication forks are possible on a bacterial chromosome. -DNA polymerase joins nucleotides in one direction (5' to 3') only. -The leading strand of DNA is made continuously. -DNA replication proceeds in only one direction around the bacterial chromosome.

DNA replication proceeds in only one direction around the bacterial chromosome.

Conjugation

Donor and recipient cells must be of an opposite mating type Requires direct contact between bacterial cells, which is typically mediated by a sex pilus

Specialized transduction

During phage infection, particular bacterial genes are transferred to the recipient

Cell-to-cell contact is required for transduction to occur. T/F

False

Transposition (insertion of a transposon into a DNA sequence) results in the formation of base substitution mutations in a cell's DNA T/F

False

During infection, C. diphtheriae grows and multiplies within the upper respiratory tract. As each bacterial cell prepares for division the chromosome must be replicated so that each daughter cell receives a copy of the genetic information. The following statements summarize the major steps in replicating the bacterial chromosome. Arrange the statements in the correct order to describe the process of replication of the leading strand. Place the following statements in the correct order of events for replication of the leading strand.

First event -Double stranded DNA is unwounded by helicase -Proteins bind to the DNA in order to stabilize the single strands -Primase synthesizes an RNA primer -DNA polymerase catalyzes formation of a sugar-phosphate bond neighboring nucleotides -Hydrogen bonds form between the complementary bases Last event

Deleting or inserting one nucleotide pair in the middle of a gene is an example of which of the following? base substitution frameshift mutation nonsense mutation missense mutation

Frameshift mutation

Which of the following is a DNA strand complementary to CGA ATC AGC? CGA ATC AGC GCU UAG UCG GCT TAG TCG TAG GCT GAT

GCT TAG TCG

How is generalized transduction different from specialized transduction?

Generalized transduction is initiated during lytic cycle of a virulent bacteriophage; specialized transduction is initiated during the lysogenic cycle of a temperate bacteriophage.

Frederick Griffith did experiments on genetic transformation. Which of the following statements about his experiments is accurate? A. Griffith used bacteria in which the nonpathogenic strain was encapsulated but the pathogenic strain was not. B. Griffith used only pathogenic bacteria in his experiments. C. The combination of living nonencapsulated bacteria and heat-killed encapsulated bacteria did not cause disease. D. Griffith found that DNA released from dead (virulent) bacteria entered live (avirulent) bacteria and changed them genetically, causing them to become virulent

Griffith found that DNA released from dead (virulent) bacteria entered live (avirulent) bacteria and changed them genetically, causing them to become virulent.

Pictured below is the inducible soap operon of the Pseudomonas species growing in the oncology ward. Imagine the operator has been damaged such that the active repressor no longer binds to it. How would this damage affect the growth of Pseudomonas?

Growth on soap would not change much, but the damage would decrease the species' growth elsewhere.

Where would one find an uncharged tRNA molecule in a ribosome?

In the P and E sites

How would one increase the concentration of a particular polypeptide in a cell?

Increase the level of transcription

Which operons are never transcribed unless activated? Inducible operons Repressible operons Inducible and repressible operons

Inducible operons

Which of the following describes how 5-bromouracil might create a mutation? -Which of the following describes how 5-bromouracil might create a mutation? -It causes double-stranded breaks of the DNA. -It can form thymine dimers. -It can replace the base thymine, and can base pair with guanine rather than adenine. -It creates bulges in the DNA that must be repaired.

It can replace the base thymine, and can base pair with guanine rather than adenine.

Which of the following are terms associated with Okazaki fragments?

Lagging strand, DNA ligase, and discontinuous

Which DNA strand is synthesized continuously?

Leading Strand

As shown in the animation, the start codon also codes for which amino acid?

Methionine

What is considered to be the average natural mutation rate that occurs during DNA replication?

One in every billion nucleotides replicated

How frequently do silent mutations occur?

One out of every three mutations

During the initiation step of translation, the fMet charged tRNA assembles in which site of the ribosome?

P site

What kind of bond is formed when two amino acids join together?

Peptide bond

Which of the following pairs is mismatched?

RNA polymerase makes a molecule of RNA from an RNA template

An enzyme that copies DNA to make a molecule of RNA is An enzyme that copies DNA to make a molecule of RNA is RNA polymerase. DNA ligase. DNA helicase. transposase. DNA polymerase.

RNA polymerase.

How does replicative transposition differ from cut-and-paste transposition?

Replicative transposition results in the transposon being copied to a new location; in cut-and-paste transposition, the entire transposon moves to the new location.

Which operons are always transcribed unless deactivated? Inducible operons Repressible operons Inducible and repressible operons

Repressible operons

Transformation

Requires the recipient cell to be competent Naked DNA is transferred from donor to recipient

Which finding is most surprising from Griffith's experiments?

S strain cells are isolated from the blood of mice infected with heat-killed S strains and live R strains.

RNA that has hydrogen bonded to itself forms a

Stem Loop

According to the operon model, for the synthesis of an inducible enzyme to occur, the end-product must not be in excess. repressor must not be synthesized. substrate must bind to the enzyme. substrate must bind to the repressor. repressor must bind to the operator.

Substrate must bind to the repressor.

Bacteria are growing in an open protein shake you placed in the refrigerator three weeks ago. The shake's ingredients include glycine and leucine—amino acids the bacteria are capable of synthesizing. The shake also contains sucrose and fructose—sugars the bacteria are capable of catabolizing. Assuming the gene expression necessary for all four of these functions is controlled by operons, which of the following statements is true? -Glycine will bind to the repressor, and the structural genes for synthesizing glycine will be expressed. -Leucine will NOT bind to the repressor, and the structural genes for synthesizing leucine will NOT be expressed. -Sucrose will bind to the repressor, and the structural genes for catabolizing sucrose will be expressed. -Fructose will bind to the repressor, and the structural genes for catabolizing fructose will NOT be expressed.

Sucrose will bind to the repressor, and the structural genes for catabolizing sucrose will be expressed.

During DNA replication, which nucleotide will bind to an A nucleotide in the parental DNA?

T

</b>Application Which of the following does NOT accurately apply to the Ames test? The test uses bacteria as mutagen carcinogen indicators. The test can be used to qualitatively test potential mutagens. The Ames test is based on the observation that reversions CANNOT occur in mutant bacteria. The Ames test measures the reversion of histidine auxotrophs of Salmonella.

The Ames test is based on the observation that reversions CANNOT occur in mutant bacteria.

According to the animation, to what genetic element does the RNA polymerase bind?

The Promoter

What most likely explains the recovery of live S strain cells from a mouse injected with heat-killed S strain mixed with live R strain cells?

The R strain picked up the S strain DNA, enabling it to produce a capsule

How does the ribosome know if the entering charged tRNA is correct?

The anticodon on the tRNA base pairs to the codon on the mRNA.

What characteristic of the S strain allows it to evade the immune system of the mice?

The cells have a capsule.

What must occur for bacterial conjugation to take place? Each cell must contain a plasmid. The cells must come into contact with each other. The cells must transfer RNA. One of the cells must be E. coli.

The cells must come into contact with each other.

The initial effect of ionizing radiation on a cell is that it causes

The formation of highly reactive ions.

If the gene that codes for transposase is mutated so that it no longer produces the fully functional enzyme, how will the insertion sequence be affected?

The insertion sequence would lose its ability to effect its own movement.

The major virulence factor produced by C. diphtheriae is diphtheria toxin. The production of diphtheria toxin during infection is controlled by a repressor, DtxR. The activity of DtxR is regulated by iron, which acts as a corepressor. During an infection, the levels of iron available in the tissues for use by C. diphtheriae are low. What effect will the decreased iron availability have on the production of diphtheria toxin

The lack of corepressor binding to DtxR will lead to a loss of repression and an increase in the production of toxin.

Which statement about DNA replication is CORRECT? -DNA ligase helps assemble the leading strand. -The leading strand is one of the strands of parental DNA. -The lagging strand is built continuously. -The leading strand is built continuously, and the lagging strand is built in pieces. -The lagging strand is one of the strands of parental DNA.

The leading strand is built continuously, and the lagging strand is built in pieces.

According to the animation, where on the DNA strand does a repressor bind? The structural genes The promoter The operator The inducer

The operator

With which genetic region does the repressor protein interact?

The operator region

What is the initial target of RNA polymerase?

The promoter

Which of the following genetic elements is transcribed into a single mRNA? The repressor The operator The structural genes The promoter The inducer

The structural genes

Why is the DNA synthesis of the lagging strand considered discontinuous?

The synthesis is moving in the opposite direction from the replication fork.

What makes an insertion sequence different from other DNA sequences found in a cell?

They are capable of effecting their own movement from one location to another on DNA.

What is the function of the connector proteins?

They link the leading strand DNA polymerase and the lagging strand DNA polymerase together.

What is the basic function of the lac operon?

To code for enzymes involved in catabolizing lactose.

What is unique about transduction compared to normal bacteriophage infection?

Transduction transfers DNA from the chromosome of one cell to another.

Which of the following is an example of horizontal gene transfer in bacteria? Transformation Conjugation Transduction Conjugation and transformation Transduction, conjugation, and transformation

Transduction, conjugation, and transformation

What is the hallmark of all horizontal gene transfers? Transfer of DNA using a virus Transfer of DNA between organisms of the same generation The use of plasmids Transfer of DNA from parent to offspring

Transfer of DNA between organisms of the same generation

Conjugation differs from reproduction because conjugation

Transfers DNA horizontally, to cells in the same generation.

What is the sequence of amino acids encoded by the following sequence of bases in a strand of DNA (pay attention to the polarity of the DNA here)? 3' ATTACGCTTTGC

Translation would stop at the first codon.

Which of the following amino acids is coded by only one codon?

Trp

Both base substitution and frameshift mutations can result in the formation of premature stop codons. T/F

True

In the Ames test, any colonies that form on the control should be the result of spontaneous mutations. T/F

True

Open-reading frames are segments of DNA in which both start and stop codons are found. T/F

True

Protein synthesis in eukaryotes is similar to the process in prokaryotes in that both eukaryotes and prokaryotes use methionine as the "start" amino acid. require snRNPS. use codons to determine polypeptide sequences. have exons. have introns.

Use codons to arrange amino acids.

How is translation terminated?

When a protein called a release factor enters and binds to the A site

A gene is best defined as -the RNA product of a transcribed section of DNA. -a sequence of nucleotides in DNA that codes for a functional product. -three nucleotides that code for an amino acid. -any random segment of DNA. -a sequence of nucleotides in RNA that codes for a functional product.

a sequence of nucleotides in DNA that codes for a functional product.

In the figure, if base 4 is thymine, what is base 4'?

adenine

Genetic change in bacteria can be brought about by conjugation. transduction. mutation. transformation. All of the answers are correct.

all of the above

Assume the two E.coli strains shown below are allowed to conjugate. Hfr: pro+, arg+, his+, lys+, met+, ampicillin-sensitive F-: pro-, arg-, his-, lys-, met-, ampicillin-resistant What supplements would you add to glucose minimal salts agar to select for a recombinant cell that is lys+, arg+, amp-resistant? ampicillin, lysine, arginine proline, histidine, methionine ampicillin, proline, histidine, lysine ampicillin, proline, histidine, methionine lysine, arginine

ampicillin, proline, histidine, methionine

GAU codes for

aspartic acid.

A nucleotide-altering chemical

can alter nitrogenous bases of DNA, resulting in incorrect base pairing.

If an indeterminate frameshift mutation occurred in the sequence of bases shown below, what would be the sequence of amino acids coded for? 3' ATTACGCTTTGC

can not tell

Competent cells are cells that

can take up DNA from their surrounding environment and integrate it into their own chromosomes by recombination.

A transducing phage

contains fragments of the host chromosome instead of the viral genome.

The damage caused by ultraviolet radiation is

cut out and replaced

A base insertion or deletion in the translated region of the gene may lead to

frameshift mutation

Which of the following enzymes unwinds the two strands of DNA so that they can be copied during replication? DNA polymerase DNA gyrase transposase helicase

helicase

The necessary ingredients for DNA synthesis can be mixed together in a test tube. The DNA polymerase is from Thermus aquaticus, and the template is from a human cell. The DNA synthesized would be most similar to

human DNA.

Mutagens -decrease the likelihood of mutations in DNA. -come in two basic forms: ionizing and nonionizing radiation. -increase the likelihood of mutations in DNA. -are the sole cause of mutations in DNA.

increase the likelihood of mutations in DNA.

Which of the following relies on a molecule binding to the repressor to prevent the repressor from binding to the operator? induction an operon gene expression repression

induction

A recombinant cell is a cell that receives DNA from an outside source and incorporates it into its own. is the result of a cell dividing. donates DNA into a new cell.

is a cell that receives DNA from an outside source and incorporates it into its own.

</b>Comprehension Which of the following best describes the flow of information in cells? -Ribosomes make proteins by randomly linking amino acids together. -mRNA is made by copying specific regions of DNA called genes. Ribosomes use mRNA as instructions, which provide a code specifying the order of amino acids in a protein. -DNA is converted to RNA, which is then converted to protein. -DNA acts as a messenger. It binds to a ribosome and provides instructions for making protein

mRNA is made by copying specific regions of DNA called genes. Ribosomes use mRNA as instructions, which provide a code specifying the order of amino acids in a protein.

Thymine dimers result from nonionizing radiation. mistakes by DNA polymerase. nucleoside analogs. ionizing radiation.

nonionizing radiation.

A base substitution that changes a codon coding for an amino acid to a stop codon is called a

nonsense mutation

A mutation that affects the genotype of the organism but not the phenotype is called a

silent mutation

How many codons code for the amino acid arginine?

six

The cancer gene ras produces mRNA containing an extra exon that includes a number of UAA codons. Cancer cells produce ras mRNA missing this exon. This mistake most likely is due to a mistake by snRNPs. DNA polymerase. UV radiation. a chemical mutagen. photolyases.

snRNPs

Mice that are injected with only the R strain of Streptococcus pneumoniae

stay healthy, because their immune systems can kill this strain easily.

RNA polymerase is guided by the

template strand of DNA

When a transducing phage interacts with a new host cell,

the DNA from the previous host can recombine with the new host chromosome.

If you knew the sequence of nucleotides within a gene, which one of the following could you determine with the most accuracy? -the quaternary structure of the protein -the tertiary structure of the protein -the secondary structure of the protein -the primary structure of the protein -The answer cannot be determined based on the information provided.

the primary structure of the protein

When the cell is not in the presence of lactose,

the repressor proteins bind to the operator.

if base 4 is thymine, what is base 11' (remember the complimentary configuration of bases in DNA)?

thymine

DNA is constructed of -two strands of identical nucleotides in a parallel configuration with hydrogen bonds between them. -a single strand of nucleotides with internal hydrogen bonding. -two strands of nucleotides running in an antiparallel configuration. -two complementary strands of nucleotides bonded AC and GT. -None of the answers is correct.

two strands of nucleotides running in an antiparallel configuration.