Microbiology 20 Chapter 9

Drug resistance can be passed between bacteria via bacteriophage in a process called transduction. Why does this usually involve only bacteria of the same species?

For transduction to occur, the phage must be able to attach to the surface of a recipient cell. Only then can it inject DNA into the cytoplasm. The initial phage binding occurs by recognition of specific surface receptors which are more likely to be the same among bacteria of the same species.

Please choose the answer that best completes the blanks of this sentence in the correct order. _______ is used to stain the endospore, and _______ is the stain used to stain the vegetative cell in spore staining.

Malachite green; safranin

Which of the following statements is true about transposons?

Sequences that flank the site of a transposon insertion are inverted repeats., The smallest transposons are often called insertion elements, Transposons can confer resistance to antibiotics., and Transposons can move from a plasmid to a chromosome.

In a chromosome, the DNA is composed of ______ strands.

2

Uracil, the nitrogenous base unique to RNA molecules, pairs with the nitrogenous base

Adenine or A

Among microorganisms, various genomes can include

All of the choices are correct.

A screening system called the __________ test is used for detecting chemicals with carcinogenic potential.

Ames

Please select all of the statements that are true about endospores.

Bacterial endospores are highly resistant to heat, drying, and radiation., Endospores can exist in the environment for indefinite periods of time., and Endospores resist boiling and therefore steam must be used to destroy endospores present in food.

Which component of DNA determines the 3' and 5' ends of the strands?

Carbons in the deoxyribose sugar

Acid-fast cells

Cells which contain a thick layer of mycolic acid or cord factor

Gram-negative cells

Cells which contain both an inner and outer membrane as well as a thin layer of peptidoglyan

The enzyme that helps pack DNA into the cell by coiling the DNA into a tight bundle is

DNA gyrase.

Which pentose sugar is found in DNA?

Deoxyribose

Which is true regarding DNA replication?

Each new DNA helix contains one parent strand and one newly synthesized strand

What is the name of the specialized plasmid that directs conjugation in gram-negative cells?

F factor

In bacterial conjugation, which term refers to a donor cell with a fertility plasmid located in the cytoplasm?

F+

Which term represents all of the genetic information within a cell?

Genome

Why is negative staining, such as a capsule stain, useful for accurately determining cell size?

Heat fixation is not performed so cells do not shrink.

Genetic inheritance in microorganisms is best defined by which term?

Heredity

What molecule is synthesized as a copy of a gene from the DNA template strand?

Messenger RNA

Which type of mutation is due to random mistakes in replication?

Spontaneous mutation

Which of the following are functions of RNA polymerase?

Synthesizes an RNA molecule from DNA template and Unwinds the DNA so that transcription can take place

Which of the following is incorrect about termination codons?

Termination codons include AUG.

How does smear preparation of cells from a liquid medium differ from preparation of cells from a solid medium?

Water is applied to the slide before emulsifying cells from a solid medium.

DNA polymerase III

adds bases to growing DNA chain

In eukaryotic cells, what cellular structure is composed of a neatly packaged DNA molecule?

chromosome

Donor and recipient bacterial cells are connected by the sex pilus during

conjugation

Which of the following is NOT a result of transposon activity in bacteria?

correction of ultraviolet radiation mutations

Which of the following is NOT a type of RNA?

dRNA

A nucleotide is oriented 5' or 3' depending on the location of the _______ on the strand of DNA.

deoxyribose carbons

conjugation

direct transfer of DNA from donor cell to recipient cell

addition or deletion of bases that changes the reading of mRNA codons

frameshift mutation

The __________ is the sum total of genetic material in a cell.

genome

The complete set of chromosomes and genes in an organism is referred to as the

genome

Which of the following is a layer found outside of the bacterial cell wall and membrane consisting of repeating sugar units and/or proteins that is resistant to staining.

glycocalyx, capsule, and slime

All of the following are methods for detecting mutant bacteria, except __________.

gram staining

A nucleosome is a linear chromosome wound around the

histone.

Base pairs in DNA are held together by __________ bonds.

hydrogen

A permanent inheritable alteration in the DNA sequence of a cell is a(n)

mutation

Extra pieces of DNA found in bacteria are called __________.

plasmids

The duplication of a cell's DNA is called

replication.

is another term for genetics--the study of inheritance in living things.

Heredity

The enzyme involved in replicating a new DNA strand is DNA polymerase _____, and DNA polymerase _____ is involved in removing the RNA primer, closing gaps, and repairing mismatched bases.

III, I

What type of mutation alters the base, but not the amino acid being coded for?

Silent

You make a smear of E. coli and then simple stain the slide with methylene blue. If you failed to use correct aseptic technique by not sterilizing the loop before picking up the bacterial sample for the smear, what results may be seen under the microscope?

There may be cells of different shapes, sizes, and arrangements.

With regard to the vanA operon, vancomycin acts as a(n):

inducer

The basic unit of DNA structure is a(n):

nucleotide

During elongation, RNA polymerase moves in a 3' to 5' direction along the __________ strand of DNA, while synthesizing a new strand of RNA in a 5' to 3'direction.

template

Why does transfer of genetic information via conjugation require direct contact between cells?

Conjugation is the process of transferring DNA from a donor to a recipient through a sex pilus. The sex pilus extends from the donor, forming a conduit through which the donor DNA may pass. Without the formation of this bridge, conjugation cannot occur. In addition, cells must remain in contact for a sufficient amount of time to enable the DNA to pass into the recipient cell.

In bacterial conjugation, which term refers to a recipient cell that does not have a fertility plasmid?

F-

All mutations are harmful to the cell.

False

Codons are found on tRNA, and anticodons are found on mRNA.

False

It is important that the smear is thick in order to ensure that the stain will be retained on the slide.

False

True or false: Bacterial conjugation is a sexual process.

False

Which DNA sequences are found within a gene but do not encode the protein specified by that gene?

Introns

Which process repairs DNA that has been damaged by ultraviolet radiation using visible light?

Photoactivation

What is a small circular segment of DNA found in the cytoplasm of prokaryotes that is capable of independent replication and usually contains nonessential genes?

Plasmid

Which recombination method involves transfer of DNA via bacteriophages?

Transduction

involves the transfer of DNA via bacteriophages.

Transduction

An enzyme that is named for its ability to build strands of DNA is DNA ________.

base

Any nitrogen-containing molecule found in DNA and RNA that provides the basis for the genetic code is a nitrogenous

base

A bacteriophage transfers random segments of DNA of the previous host to the current host. This is an example of

generalized transduction.

When one bacterium donates DNA to another bacterium, a type of genetic recombination known as __________ has occurred.

horizontal gene transfer

The DNA of microorganisms is made up of subunits called

nucleotides.

Hfr transfer involves all of the following except

plasmid gene transfer.

Mutations that involve the addition, deletion or substitution of one or a few bases are referred to as _______ mutations.

point

DNA _______ is the enzyme responsible for building strands of DNA.

polymerase

DNA polymerase I

removes RNA primers, replaces with DNA bases

transduction

transfer of DNA via phage

"Jumping genes" are known as

transposons

Genes that jump from one location to another in the genome are

transposons.

helicase

unzips the DNA double helix

transformation

uptake of free DNA

Which base will pair with uracil in RNA?

Adenine

One reason mutations are so problematic is that bacterial cells have no ability to repair a mutation once it has occurred.

False

The genomes of bacteria cells, eukaryotic cells, and viruses are all about the same size.

False

Transformation is a mode of genetic recombination in which a plasmid is transferred from a donor cell to a recipient cell via a direct connection.

False

True or false: In bacterial conjugation, all F+ donor cells are high frequency recombinant (Hfr) cells.

False

True or false: Mutations are always harmful to cells.

False

Which is the correct order of events when a protein is made in the process of translation?

Initiation, elongation, termination

Which of the following is incorrect about transfer RNA?

Initiator tRNA in bacteria carries tryptophan.

are DNA sequences found within a gene that do not encode the protein corresponding to the gene.

Introns or Intron

If the wild type DNA sequence reads THE CAT ATE THE BIG RAT, what type of mutation would change the sequence to THE CAT ATE THE BAG RAT?

Missense

Which of the following are parts of a nucleotide in DNA?

Nitrogenous base, Phosphate, and Deoxyribose sugar

Which nitrogenous base is found in RNA but not found in DNA?

Uracil

Given the description of how the expression of vanA is regulated, what best describes the role of vancomycin in gene regulation? Describe a regulatory scheme for vanA.

In this case, vancomycin acts as an inducer. In the absence of vancomycin, a repressor protein prevents the expression of vanA by binding to the promoter and blocking RNA polymerase. When vancomycin is present, it binds to an allosteric site of the repressor, causing a conformational change that releases the repressor from the DNA. This allows RNA polymerase to proceed with transcription of vanA.

The main enzyme responsible for transcription is

RNA polymerase.

What must occur prior to cell division to ensure that each new cell has a complete set of DNA chromosome(s)?

Replication

What cell structure is responsible for protein synthesis?

Ribosome

mutations in DNA are caused by random mistakes in replication and not known to be influenced by any mutagenic agent.

Spontaneous

Clinicians identifed a new drug-resistant bacteria in a patient's foot wound. The gene responsible for the drug resistance was flanked by DNA sequences that are inverted repeats of one another. What is the most probable way that this bacteria acquired the gene for drug resistance?

The gene was part of a transposon.

True or false: Several codons code for the same amino acid, which is called the redundancy of the code.

True

Choose all of the statements that are true about the potential impact of missense mutations.

create nonfunctional proteins, produce proteins with altered function, and have no impact on protein function

Based on the concept of "Relative Resistance of Microbial Forms" to microbial control methods (review Chapter 11, Section 11.1 for an explanation of relative resistance), the CRE bacteria in this case would be classified as _______ with respect to microbial control methods.

least resistance

Which of the following types of RNA is the transcribed version of a structural gene in DNA, that is later read for translation into protein?

mRNA

Which of the following are directly needed in order for translation to occur?

mRNA, tRNA, rRNA, and amino acids

gyrase

mediates supercoiling

Split genes

require spliceosomes to excise introns and then join exons.

The pentose sugar found in RNA is

ribose

forms a complex cellular structure that contributes to the process of translation

ribosomal RNA

ligase

seals nicks in DNA backbone during synthesis and repair

Nucleotides can only be added to the ____ end of a growing chain.

3'

All new DNA strands are synthesized from

5' to 3'.

If a codon of mRNA reads 5'-UUG-3', the tRNA that delivers the amino acid to this location during translation will have an anticodon of 3'-_____-5'.

AAC

Which type of plasmids confer the ability of an organism to survive treatment by antibiotics?

R factors

Which term refers to the transfer of genes from donor to recipient microorganisms?

Recombination

Which pentose sugar is found in RNA?

Ribose

Which of the following is not true of the prokaryotic ribosome?

The small subunit provides the enzymes for making peptide bonds.

What is the purpose of the Ames test?

To determine the carcinogenic potential of a chemical

DNA polymerase III is responsible for:

building the DNA chain

A mutation that causes a change in a single nucleotide in DNA

changes the corresponding nucleotide in mRNA, resulting in a different codon.

The pentose sugar found in DNA is

deoxyribose

Spontaneous mutations result from errors in DNA replication, while __________ mutations are caused by exposure to known mutagens that damage DNA.

induced

result from exposure to known mutagens, which are primarily physical or chemical agents that damage DNA

induced mutation

The __________ subunit of the ribosome is the site of peptide bond formation.

large

Please choose the answer that best fills in the blanks of this sentence in the correct order. Gram-________ cells stain purple whereas gram-_______ cells stain pink or red when using the Gram stain technique.

positive; negative

DNA polymerases are responsible for

proofreading/repair. and building the DNA chain.

In bacteria, mRNA transcripts are first recognized by the __________ subunit of the ribosome.

small

The enzyme __________ is responsible for compacting the DNA molecule in prokaryotes.

topoisomerase

contains the anticodon and an amino acid binding site

transfer RNA

The RNA molecules that carry amino acids to the ribosomes during protein synthesis are called

transfer RNA.

The acceptance by a bacterial cell of small DNA fragments from the surrounding environment is termed __________.

transformation

During which method of gene transfer are bacterial cells in direct contact?

Conjugation

R factors are specifically associated with which mechanism of recombination?

Conjugation

in bacteria refers to horizontal gene transmission via pili.

Conjugation

Which best describes the flow of genetic information in a cell?

DNA encodes RNA which encodes protein

The process of natural transformation was first discovered with experiments involving the Gram-positive bacterium Streptococcus pneumoniae. Which of the following statements is true about transformation of S. pneumoniae?

DNA fragments must bind to cell surface receptors prior to uptake. and Transformation can be used to produce genetically engineered organisms.

are able to shift from one part of the genome to another.

Transposons

Gram-positive cells

Cells which contain a thick layer of peptidoglycan and teichoic acids

In bacterial conjugation, which type of donor has the fertility factor integrated into the chromosome?

Hfr

DNA polymerase ____ is the main enzyme involved in the building of the new DNA chain, whereas DNA polymerase ____ is involved mostly with removing the primers and repairing damaged DNA.

III/I

refers to the transfer of genes from donor to recipient microorganisms, where the recipient strain shows a change in genetic makeup at the end.

Recombination

Please choose all of the statements that are true regarding transcription and translation in prokaryotes.

Prokaryotic mRNAs often contain information from several genes in series., Transcription and translation can occur at the same time in prokaryotes., and Translation occurs in the cytoplasm of prokaryotes.

Which of the following best describes translation?

RNA -> protein

The large enzyme complex involved in synthesizing RNA from a DNA template is called

RNA polymerase

The large enzyme complex involved in synthesizing RNA from a DNA template is which of the following?

RNA polymerase

Select the statements that represent goals in correct smear preparation.

The cells must be heat fixed to the slide to prevent removal when stain is washed off the slide., It is important to minimize any artifacts or distortion of the cells for accurate viewing after staining., and Smears must be thin to allow for observation of single cells.

You observe this slide under the microscope. It was prepared with a negative stain used to visualize capsules.

This bacterium is encapsulated., The bacterial cells are dark purple., and The capsules are white spaces around dark cells in this field.

Which gene transfer method involves the uptake of free DNA by competent bacterial cells?

Transformation

involves the uptake of free DNA by competent bacterial cells.

Transformation

Another method by which bacteria can gain drug resistance is through transposons. These mobile genetic elements are sometimes referred to as "jumping genes". Describe why this is the case.

Transposons are pieces of DNA that can move to many different positions within or between pieces of DNA. Transposons encode two key enzymes—transposase and resolvase—which allow it to excise itself and integrate itself almost anywhere in a piece of DNA. This can result in a transposon moving between different regions of a chromosome, or between a chromosome and a plasmid.

Which term, synonymous with codon, describes a trinucleotide sequence coding an amino acid in DNA?

Triplet

DNA is the blueprint that indicates which kinds of proteins to make and how to make them.

True

DNA mutations are passed on to a cell's progeny.

True

DNA photolyase is a light-sensitive enzyme able to repair DNA damaged by ultraviolet radiation.

True

The capsule can be considered a virulence factor and microorganisms containing one are often pathogenic.

True

True or false: A mutation is an alteration in the DNA sequence or content of a cell that is passed on when the cell divides.

True

True or false: R-factors or "resistance factors" can be shared between bacteria through conjugation to help them survive the effects of antibiotics.

True

In RNA, which nitrogenous base pairs with adenine?

Uracil

Vancomycin is used to treat infections with Gram-positive bacteria like Staphylococcus aureus, but not Gram-negative bacteria like Escherichia coli. Why do you think this is the case?

Vancomycin inhibits cell wall biogenesis by inhibiting cross-linking via the terminal D-Ala-D-Ala peptide stem. Vancomycin is also a rather large, hydrophilic molecule. The presence of the outer membrane in Gram-negative bacteria prevents vancomycin from reaching the cell wall. In contrast, Gram-positive bacteria do not have a barrier to protect their cell wall.

Genetic transfer of ______ to a methicillin-resistant Staphylococcus aureus (MRSA) strain produces vancomycin resistant enterococci (VRE).

a transposon containing the vanA operon

Replication of DNA begins at a/an

adenine-thymine rich area.

Groups of three consecutive bases along the DNA of a gene have the code for one

amino acid.

Proteins that remove incorrect bases and replace them with correct ones are termed ______ repair enzymes.

excision

transcribed version of a structural gene or genes in DNA

messenger RNA

Genetic __________ and the variations they produce result in population changes and thus, evolution.

mutations

A _______ stain is one that colors the background surrounding the cell, leaving the cell itself unstained.

negative

The place where DNA replication is initiated is called the ______.

origin of replication

DNA replication is said to be

semi-conservative.

random change in the DNA arising from errors in replication that occur without a known cause

spontaneous mutation

When the ribosome reaches one of three different __________, it stops protein synthesis and the finished polypeptide chain is released.

stop codons

changing of single base in the DNA code that may result in the placement of a different amino acid

substitution mutation

DNA gyrase

supercoils DNA.

primase

synthesizes RNA primers

Which of the following types of RNA delivers the amino acids to the growing peptide chain in translation?

tRNA