microbiology ch. 7 homework – Flashcards
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What are the products of semiconservative replication for a double-stranded DNA molecule?
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Two double-stranded DNA molecules, each consisting of one parental strand and one daughter strand.
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Why is DNA replication essential for a cell?
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An organism must copy its DNA to pass genetic information to its offspring.
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What is the function of the parental DNA in replication?
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It serves as the template for DNA replication.
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Which of the following build(s) new strands of DNA?
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DNA polymerases
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Which statement about DNA replication is CORRECT?
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The leading strand is built continuously, and the lagging strand is built in pieces.
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the leading strand is built _______ but the lagging strand
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continuously
lagging strand is built in pieces
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The molecule that seals the gaps between the pieces of DNA in the lagging strand is
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DNA ligase.
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What characteristic of DNA allows two connected DNA polymerases to synthesize both the leading and lagging strands?
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DNA is flexible.
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What is the function of the connector proteins?
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They link the leading strand DNA polymerase and the lagging strand DNA polymerase together.
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Which DNA strand is synthesized continuously?
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Leading strand
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Which of the following are terms associated with Okazaki fragments?
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Lagging strand, DNA ligase, and discontinuous
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Why is the DNA synthesis of the lagging strand considered discontinuous?
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The synthesis is moving in the opposite direction from the replication fork.
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The process of making a complementary copy of DNA into the form of RNA is called __________.
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transcription
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Which of the following characteristics of a chromosome would identify it as a prokaryotic chromosome rather than a eukaryotic chromosome?
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It is a circular molecule.
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Which of the following is necessary for conjugation to occur?
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a conjugation pilus
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Bacteriophages are important for which of the following processes?
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transduction
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mRNA, tRNA, and rRNA are all produced by ___________.
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produced by transcription.
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According to the animation, which of the following makes mRNA from the information stored in a DNA template?
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RNA polymerase
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Ribosomes contain which of the following?
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rRNA
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Which of the following is involved in bringing amino acids to the ribosomes?
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tRNA
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Which of the following can be translated into protein?
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mRNA
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What is the initial target of RNA polymerase?
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The promoter
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RNA polymerase is guided by the
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template strand of DNA.
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RNA that has hydrogen bonded to itself forms a
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stem loop.
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How would one increase the concentration of a particular polypeptide in a cell?
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Increase the level of transcription
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During elongation, how is the RNA synthesized?
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5' to 3'
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What results from the process of translation?
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A polypeptide
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How is bacterial translation different from eukaryotic translation?
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Bacteria can begin translation before transcription has terminated.
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According to the animation, ribosomes move along the mRNA in which direction?
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5' to 3'
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During the initiation step of translation, the fMet charged tRNA assembles in which site of the ribosome?
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P site
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How does the ribosome know if the entering charged tRNA is correct?
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The anticodon on the tRNA base pairs to the codon on the mRNA.
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Where would one find an uncharged tRNA molecule in a ribosome?
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In the P and E sites
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What kind of bond is formed when two amino acids join together?
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A peptide bond
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How is translation terminated?
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When a protein called a release factor enters and binds to the A site
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Which of the following events occurs during transcription?
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A molecule of RNA is formed based on the sequence of nucleotides in DNA.
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Which of the following is a correct statement about mRNA?
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mRNA moves from the nucleus to the cytoplasm following RNA processing.
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The site of translation is
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ribosomes in the cell cytoplasm.
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Which one of the following does not play a role in translation?
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DNA
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Which of the following does not occur during RNA processing?
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mRNA attaches to the small subunit of a ribosome.
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Some eukaryotes have plasmids in their cytoplasm, as well as circular DNA molecules within their chloroplasts and mitochondria. true or false
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true
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Eukaryotic ribosomes bind to the 5' guanine cap, while bacterial ribosomes bind to a specific nucleotide sequence.
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true
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The process of copying DNA genetic information into the form of RNA is called __________.
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transcription
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Which of these describes the function of the lactose (lac) operon?
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It ensures that bacteria only make the enzymes to catabolize lactose when lactose is present.
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Which of the following types of mutations always creates a stop codon where one did not exist before?
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nonsense mutation
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Insertions and deletions usually lead to which of the following types of mutations?
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frameshift mutations
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The Ames test involves mutants of Salmonella that __________ the ability to make histidine in the __________ of a suspected mutagenic chemical.
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gain; presence
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Mutagens
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increase the likelihood of mutations in DNA.
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A nucleotide-altering chemical
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can alter nitrogenous bases of DNA, resulting in incorrect base pairing.
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What is considered to be the average natural mutation rate that occurs during DNA replication?
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One in every billion nucleotides replicated.
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A mutation that affects the genotype of the organism but not the phenotype is called a
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silent mutation.
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A base insertion or deletion in the translated region of the gene may lead to
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frameshift mutation.
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A base substitution that changes a codon coding for an amino acid to a stop codon is called a
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nonsense mutation.
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How frequently do silent mutations occur?
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One out of every three mutations
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A silent mutation is so named because __________.
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it has no effect on the overall amino acid sequence
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Which of the following types of mutations creates a stop codon where one did not exist before?
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nonsense mutation
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Insertions and deletions usually lead to which of the following types of mutations?
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frameshift mutations
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X rays and gamma rays cause which of the following types of problems in DNA?
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physical breaks in chromosomes
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A(n) ________ is a mutant organism that has different nutritional requirements from the original wild-type organism.
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auxotroph
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The most common type of mutation is a point mutation.
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True
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What process involves copying sequences of DNA nucleotides into sequences of RNA nucleotides?
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transcription
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An initiator transfer RNA (tRNA) binds to the __________ of the small ribosomal subunit during the initiation of translation.
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P site
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The _______ is the area of the small ribosomal subunit where the initiator ________ will bind during the initiation of translation.
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P site, tRNA
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Transfer RNA (tRNA) is responsible for transporting a(n) __________.
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amino acid
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tRNA transports what?
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amino acids
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The energy used to bind transfer RNA (tRNA) to a ribosome's P site comes directly from __________.
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GTP
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The energy stored in the bonds of _____ is used to bind tRNA to the P site of a ribosome
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GTP
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in bacteria, what amino acid is transported by the initiator tRNA?
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fMet (formylmethionine)
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Nucleotide bases form __________ bonds with their complementary bases.
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hydrogen
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The first step in the initiation of translation involves the attachment of the __________ to the start codon of the messenger RNA (mRNA).
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small ribosomal subunit
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Which of the following genetic elements is transcribed into a single mRNA?
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The structural genes
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Which operons are always transcribed unless deactivated?
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Repressible operons
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Which operons are never transcribed unless activated?
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Inducible operons
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According to the animation, where on the DNA strand does a repressor bind?
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The operator
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What is the inducer molecule in the lac operon?
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Allolactose
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With which genetic region does the repressor protein interact?
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The operator region
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When the cell is not in the presence of lactose,
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the repressor proteins bind to the operator.
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What is the basic function of the lac operon?
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To code for enzymes involved in catabolizing lactose.
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According to the animation, to what genetic element does the RNA polymerase bind?
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The promoter
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When is the repressor protein transcribed?
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It is always transcribed.
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Why is the tryptophan operon turned off in the presence of tryptophan?
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Tryptophan binds to and activates the repressor proteins; the repressor proteins, in turn, bind to the operator, preventing transcription.
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According to the animation, how do the repressor proteins block the transcription of the structural genes?
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It binds to the operator when activated.
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an operon is
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a set of prokaryotic genes that are regulated and transcribed as a unit.
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A recombinant cell
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is a cell that receives DNA from an outside source and incorporates it into its own.
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What is the hallmark of all horizontal gene transfers?
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Transfer of DNA between organisms of the same generation
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Which of the following is an example of horizontal gene transfer in bacteria?
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Transduction, conjugation, and transformation
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Competent cells are cells that
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can take up DNA from their surrounding environment and integrate it into their own chromosomes by recombination.
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Which of the following statements is true of bacterial plasmids?
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They are small circular DNA molecules that can replicate autonomously.
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Bacterial conjugation is often referred to as bacterial sex. Why is this term inaccurate?
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Conjugation does not result in the formation of new offspring.
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What must occur for bacterial conjugation to take place?
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The cells must come into contact with each other.
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Which statement about conjugation is false?
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Conjugation is a process of bacterial reproduction.
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Based on the animation, what is transferred during bacterial conjugation?
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A bacterial plasmid
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What is the function of the conjugation pilus?
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It pulls the F+ and F- cells together.
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What is required by an F- cell to become an F+ cell?
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F plasmid
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What is the key difference between donor cells and recipient cells?
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An F plasmid
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What cellular macromolecule is the fertility factor comprised of?
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Nucleic acid
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At which point does a recipient cell become an F+ cell?
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Formation of the complementary strand of the F factor
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How does an F+ cell differ from an Hfr cell?
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Hfr strains have the F plasmid integrated into the chromosome.
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Which of the following is a characteristic of an F+ cell?
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Ability to synthesize sex pili, presence of a fertility factor, and ability to mate with an F- cell.
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What benefit does the F- strain receive from mating with an Hfr strain?
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It acquires new, potentially beneficial genes from the Hfr strain.
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What is unique about transduction compared to normal bacteriophage infection?
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Transduction transfers DNA from the chromosome of one cell to another.
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How is generalized transduction different from specialized transduction?
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Generalized transduction is initiated during lytic cycle of a virulent bacteriophage; specialized transduction is initiated during the lysogenic cycle of a temperate bacteriophage.
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A transducing phage
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contains fragments of the host chromosome instead of the viral genome.
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When a transducing phage interacts with a new host cell,
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the DNA from the previous host can recombine with the new host chromosome.
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How does specialized transduction differ from regular lysogeny?
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The prophage in specialized transduction carries with it pieces of the host chromosomal DNA.
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What happens to the packaged DNA of a specialized transduced phage when it infects a new recipient cell?
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The host DNA integrates, with the prophage, into the new recipient chromosome.
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How can specialized transduction contribute to the transfer of antibiotic resistance genes in a bacterial population?
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The prophage takes an antibiotic resistance gene with it and is packaged with the newly synthesized viral DNA.
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Insertion sequences target which areas on a target DNA sequence?
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A sequence of nucleotides identical to the inverted repeat sequence found on the insertion sequence itself
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What makes an insertion sequence different from other DNA sequences found in a cell?
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They are capable of effecting their own movement from one location to another on DNA.
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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?
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The insertion sequence would lose its ability to effect its own movement.
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How does replicative transposition differ from cut-and-paste transposition?
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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.
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How is a complex transposon different from a simple transposon?
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They have two simple transposons with another DNA sequence between them.
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Why does a complex transposon often contain an extra piece of DNA between the two insertion elements?
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It is often a gene that confers a survival advantage to the host, such as antibiotic resistance.
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A mutation that causes production of a defective pilus in a bacterium will prevent __________.
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conjugation
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What was the significance of Frederick Griffith's experiments with Streptococcus pneumoniae?
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He showed that the DNA from strain S cells could transform strain R cells.
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Bacteriophages are important for which of the following processes?
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transduction
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transduction
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Transfer of DNA between cells by viruses
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The horizontal transfer process known as transduction
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involves a virus.
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Most bacteria have a natural ability to take up DNA from their environment.
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False
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In generalized transduction, viruses carry random DNA sequences from one cell to another.
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true
