BIO 208

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.

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

GM crops have raised issues among communities in which they are produced. Which of the following are concerns raised by the public about genetically engineered crops?

-The Bt gene could ultimately make the plants pathogenic to humans. -The Bt toxin could result in the death of non-pest species of insects. -The Bt toxin could negatively affect the taste of the food that is produced from these crops.

How many colony forming units (CFUs) are in the original tube per mL if you ran a serial 10 dilution and counted 230 colonies on the 1:100,000 dilution plate?

230x10^5

If all the following DNA fragments were analyzed on an electrophoresis gel, which one would migrate farthest from the negative electrode?

250 base pairs

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

3' UCA 5'.

At which point does a recipient cell become an F+ cell? 1. Fusion of the cell membranes 2. Attachment of the sex pilus 3. Transfer of the single stranded F factor 4. Pulling of donor and recipient cells together 5. Formation of the complementary strand of the F factor

5.

If argG, argR, and argE are all required to make a cell able to metabolize arginine, how long would it take for an arg- recipient to become arg+?

87

Based on the animation, what is transferred during bacterial conjugation?

A bacterial plasmid

What is a boil?

A boil is a red lump in the skin that may be warm and painful to the touch. It is a localized accumulation of pus and tissue debris.

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?

AUU CGC AUC UUG AAC

Which of the following is a characteristic of an F+ cell?

Ability to synthesize sex pili, presence of a fertility factor, and ability to mate with an F- cell.

Which of the following microbes produces a protein that kills a variety of insect pests?

Bacillus thuringiensis

Which of the following might result in a frameshift mutation?

Benzopyrene

Which type of transposon would contain a gene for transposase?

Both simple and complex transposons

Which of the following statements concerning sticky-ended fragments is most likely to be true?

Complementary sticky-ended fragments were probably cut by the same restriction enzyme.

How do complex transposons differ from simple transposons?

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?

Conjugation does not result in the formation of new offspring.

Which statement about conjugation is false?

Conjugation is a process of bacterial reproduction.

Why does conjugation between an Hfr strain and an F- strain not result in two Hfr strains?

Conjugation is typically disrupted before the fertility factor can be transferred.

Which of the following seals the sticky ends of restriction fragments to make recombinant DNA?

DNA ligase

How are restriction enzymes named?

Each is named with letters referring to the genus, species, and strain of the source prokaryote and a Roman numeral denoting the order of its discovery.

What is required by an F- cell to become an F+ cell?

F plasmid

What does the term facultative anaerobe mean?

Facultative anaerobes can grow with or without oxygen. More growth is evident when oxygen is present.

If gene X transferred at 99 minutes for E. coli, what conclusion could you make about gene X?

Gene X is close to the fertility factor on the Hfr chromosome, but is near the end of the chromosome transfer.

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.

Bt crops, including potatoes and cotton, are genetically engineered using laboratory techniques. Which of the following utilizes recombinant DNA technology to produce advantageous traits in the crops that are produced?

Genetically engineered crops have an advantageous gene from another organism inserted into their genome.

How does an F+ cell differ from an Hfr cell?

Hfr strains have the F plasmid integrated into the chromosome.

How can hospital personnel prevent the spread of resistant E. faecium throughout the hospital?

Hospital personnel should wash their hands when entering and leaving a patient's room.

Bt crops are engineered in the lab to produce Bt toxins due to the presence of a bacterial gene from B. thuringiensis. Why is it advantageous for the plants to produce the Bt toxin?

Insects that normally destroy non-toxin-producing crops will be killed when they eat plants that do produce the toxin.

What benefit does the F- strain receive from mating with an Hfr strain?

It acquires new, potentially beneficial genes from the Hfr strain.

How does aspirin act to decrease the symptoms of inflammation?

It blocks the release of histamine.

Which of the following describes how 5-bromouracil might create a mutation?

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

What is the effect of a nonsense mutation in a gene?

It introduces a premature stop codon into the mRNA.

What does halophilic mean?

It means the organism is "salt loving".

Why might a point mutation in DNA make a difference in the level of protein's activity?

It might substitute an amino acid in the active site.

How does conjugation help geneticists map the genomes of bacteria?

It provides them with the relative positions of the genes on the chromosomes.

What is the function of the conjugation pilus?

It pulls the F+ and F- cells together.

A student states that the trp gene is located at 26 minutes. What does this mean?

It takes 26 minutes for the gene to be transferred during conjugation.

What does the term mesophile mean?

Mesophiles grow well at 85 degrees Celsius.

Which of the following repair enzymes cannot repair thymine dimers?

Mismatch-repair enzymes

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

Which of the following is true for both prokaryotic and eukaryotic gene expression?

RNA polymerase binds to the promoter region to begin transcription.

In which of the following actions does RNA polymerase differ from DNA polymerase?

RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis.q

Which of the following statements best describes the termination of transcription in prokaryotes?

RNA polymerase transcribes through the terminator sequence, causing the polymerase to fall off the DNA and release the transcript.

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.

Assume that Staphylococcus aureus grows on nutrient agar with up to and including 15% (w/v) NaCl, while Escherichia coli cannot grow on nutrient agar with more than 10% (w/v) NaCl. What does this mean?

Some kinds of bacteria can grow at higher concentrations of NaCl than others.

Which of the following methods uses DNA probes?

Southern blot

Which organism is most likely to be responsible for the boils?

Staphylococcus aureus

Which of the following bacteria have an affinity for the heart valves?

Streptococcus mutans

Each of the following options is a modification of the sentence THECATATETHERAT. Which of the following is analogous to a frameshift mutation?

THECATATTHERAT

Which of the following best explains how scientists are able to introduce the bacterial gene for Bt toxin into the cotton plant genome?

The Bt toxin gene is isolated and inserted into a Ti plasmid from Agrobacterium tumefaciens. The engineered Ti plasmid is taken up by a bacterium that infects the cotton plant.

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.

What is unique about transduction compared to normal bacteriophage infection?

The bacteriophage takes fragments of the cell with it during transduction.

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?

The cells must come into contact with each other.

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.

Why is light required for photolyases?

The light provides the energy to break the bonds between the thymine dimers.

How is DNA methylation used in DNA repair?

The mismatch-repair enzymes can use a lack of methylation to identify and remove newly synthesized DNA.

All restriction sites are palindromic. What does this mean?

The nucleotide sequences at the restriction sites are the same when read forward or backward.

As a ribosome translocates along an mRNA molecule by one codon, which of the following occurs?

The tRNA that was in the A site moves into the P site.

What action do restriction enzymes employ?

They cut DNA.

What role do restriction enzymes serve in the prokaryotes that produce them?

They destroy viral DNA.

What is a nosocomial infection?

This is a hospital-acquired infection.

In the 1920s Muller discovered that X-rays caused mutation in Drosophila. In a related series of experiments, in the 1940s, Charlotte Auerbach discovered that chemicals (she used nitrogen mustards) ave a similar effect. A new chemical food additive is developed by a cereal manufacturer. Why do we test for its ability to induce mutation?

We want to prevent any increase in mutation frequency.

Of the following, which is the most current description of a gene?

a DNA sequence that is expressed to form a functional product: either RNA or polypeptide

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?

a deletion of 2 nucleotides

The genetic code is essentially the same for all organisms. From this, one can logically assume all of the following except

a gene from an organism could theoretically be expressed by any other organism.

Transfer RNA (tRNA) is responsible for transporting a(n) __________.

amino acid

What is the key difference between donor cells and recipient cells?

an F plasmid

When does translation begin in prokaryotic cells?

as soon as transcription has begun

The restriction enzyme KpnII probably originated __________.

as the second discovered restriction enzymes from Klebsiella pneumoniae bacterium

The energy used to bind transfer RNA (tRNA) to a ribosome's P site comes directly from __________.

atp

Which of the following is an example of a biofilm?

bacteria growing in plaque

The role of a metabolite that controls a repressible operon is to

bind to the repressor protein and activate it.

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the

bonding of the anticodon to the codon and the attachment of amino acids to tRNAs.

A nucleotide-altering chemical

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

Competent cells are cells that

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

What term is used to describe bacterial cells that can naturally take up DNA from their environment?

competent cells

Transgenic organisms

contain genes from other organisms

A transducing phage

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

A mutation that inactivates the regulatory gene of a repressible operon in an E. coli cell would result in

continuous transcription of the structural gene controlled by that regulator.

Which of the following is NOT used by bacteria to acquire new genetic material?

crossing over

Assume that you are trying to insert a gene into a plasmid. Someone gives you a preparation of genomic DNA that has been cut with restriction enzyme X. The gene you wish to insert has sites on both ends for cutting by restriction enzyme Y. You have a plasmid with a single site for Y, but not for X. Your strategy should be to

cut the DNA again with restriction enzyme Y and insert these fragments into the plasmid cut with the same enzyme.

During log phase, bacteria are:

dividing at the fastest possible rate.

What is one method by which you could insert DNA from one cell into another cell?

electroporation

Once transcribed, eukaryotic mRNA typically undergoes substantial alteration that includes

excision of introns.

A new chemotherapeutic agent is developed that alters the structure of all thymines in DNA. These thymines are then misread during the production of mRNA. Which of the following could NOT result from this type of mutation?

frameshift mutation

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

frameshift mutation.

Which of the following separates molecules by movement due to size and electrical charge?

gel electrophoresis

a facultative anaerobic bacteria species such as Escherichia coli will exhibit what characteristics when grown in a broth tube?

growth throughout the tube with the highest concentration at the top

An organism found at the bottom of the Dead Sea is most likely a ____________.

halophile microaerophile barophile

Nucleotide bases form __________ bonds with their complementary bases.

hydrogen

mutagens

increase the likelihood of mutations in DNA.

The first and second lines of defense against microbial invasion are part of

innate immunity

The horizontal transfer process known as transduction

involves a virus.

A silent mutation is so named because __________.

it has no effect on the overall amino acid sequence

If conjugation was allowed to be carried out for 25 minutes, which genes would be transferred to the recipient strain?

lac

Which of the following terms is likely to describe optimal growing conditions for Streptococcus mutans?

mesophile

You isolate a pure culture and determine that its CHARACTERISTICS are as follows. It GROWS optimally at 28°C. It will SURVIVE at temperatures from -70°C to +35°C. Its pH OPTIMUM for growth is 7.2. It was originally ISOLATED on the surface of strawberry jam. You might correctly CONCLUDE that this microbe is a(n) __________.

mesophilic aerobe that resists plasmolysis when sugar concentration is high.

The initiator transfer RNA (tRNA) in bacteria has the anticodon sequence UAC and transports the amino acid __________.

met

What does MDR mean?

multi-drug-resistant

Thymine dimers result from

nonionizing radiation

While studying protein synthesis in the lab, you experimentally induce a mutation in a bacterium's DNA. You assess the proteins in the mutated bacterium and find that one of them is significantly shorter than its wild-type counterpart. Based on this information, what type of mutation did you induce?

nonsense mutation

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

nonsense mutation.

What cellular macromolecule is the fertility factor comprised of?

nucleic acid

An initiator transfer RNA (tRNA) binds to the __________ of the small ribosomal subunit during the initiation of translation.

p site

The evolutionary history of a group of organisms is called:

phylogeny

A mutation in this section of DNA could influence the binding of RNA polymerase to the DNA:

promoter

A mutant bacterial cell has a defective aminoacyl synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of a phenylalanine. The consequence of this for the cell will be that

proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.

Which of the following is NOT a vector?

protoplast fusion

What is the most abundant type of RNA?

rRNA

Which of the following types of media is designed to suppress the growth of unwanted bacteria and encourage the growth of desired microbes?

selective media

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

silent mutation.

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

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

Which nutrient is responsible for the development of cavities in teeth?

sucrose

The first step in the initiation of translation involves the attachment of the __________ to the start codon of the messenger RNA (mRNA).

tRNAfMet

When a transducing phage interacts with a new host cell,

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

What does the operon model attempt to explain?

the coordinated control of gene expression in bacteria

If growing a new bacteria culture for testing cellular metabolism, which phase would be best to take the bacteria from?

the lag phase

From the following list, which is the first event in translation in eukaryotes?

the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA

Although blunt-ended DNA fragments are more difficult to join back together than are sticky ends, blunt ends have an advantage in that __________.

they can be recombined with blunt fragments produced by different restriction enzymes

In the laboratory, recombinant DNA technologists use restriction enzymes __________.

to cut specific genes from one organism for the purpose of inserting the genes into the DNA of another organism

What process involves copying sequences of DNA nucleotides into sequences of RNA nucleotides?

transcription

A turbidity meter can be set to distinguish between living and dead cells

true

During the lag phase, the bacterial cells are dormant and metabolically inactive

true

Identify the anticodon complementary to the start codon with sequence AUG.

uac

Which one of the following is not a characteristic of prokaryotes?

uses mitosis