CH 7: Mastering Microbiology
In general, higher levels of transcription lead to ______________________.
higher amounts of protein.
CAU codes for ___________________.
histidine
Which of the following would be a fate of a bacterium infected by a generalized transducing bacteriophage?
integration of the packaged DNA into the host chromosome
X-rays would be considered which type of mutagen?
ionizing radiation
The replication fork __________________.
is the point where DNA helicase is "unzipping" the double-stranded DNA molecule.
A mutation that results in the presence of a stop codon in the middle of the genetic code is a _____________.
nonsense mutation.
DNA replication is a polymerization reaction that requires all of the following __________.
nucleotide monomers a source of energy to form covalent bonds six classes of enzymes
How frequently does an error occur in DNA replication in the absence of a mutagen?
one error for every 1,000,000,000 nucleotides copied
Which of the following are genetic elements found in an operon?
operator region structural genes promoter
Which of the following is used to make ribosomes?
rRNA
Which of the following terms could describe the newly infected host of a specialized transducing bacteriophage?
recipient cell recombinant cell
A cell that has incorporated new DNA as part of its own is termed a __________.
recombinant
What does the inducer bind to in the lac operon system?
repressor proteins
The process of generalized transduction ___________.
requires a lytic bacteriophage. utilizes any fragment of the bacterial chromosome. results from sloppy packaging of DNA by bacteriophage.
All of the following are a type of RNA involved in polypeptide synthesis
ribosomal RNA, which is the nucleotide component of ribosomes messenger RNA, which carries information from chromosomes as triplet sequences transfer RNA, which is folded to allow base pairing and is charged with an amino acid specific for its anticodon
Which of the following is involved in translation?
ribosomes mRNA amino acids
During the elongation step of translation, which of the following forms the peptide bond between the terminal amino acid and the newly introduced amino acid?
ribozyme
Thymine dimers may result from exposure to ultraviolet light. What kind of mutation is associated with pyrmidine dimers?
silent
Which mutation is the least likely to be harmful to a cell?
silent mutation
Base pair substitutions can result in what type(s) of mutation?
silent, nonsense, and missense
Which of the following is involved in bringing amino acids to the ribosomes?
tRNA
The anticodon sequence is found on the __________.
tRNA.
An amino acid is considered charged ____________.
when it is bound to its correct tRNA.
The tryptophan operon is described as repressible because __________.
when tryptophan is available, it activates a repressor that blocks transcription
Place the following events of lagging strand DNA synthesis in order: DNA polymerase synthesizes new DNA strand in the 5' to 3' direction. Primase adds an RNA primer. Okazaki fragments are joined together. RNAse removes the RNA primer.
2, 1, 4, 3
According to the chart, how many amino acids are coded for by codons?
20
How many codons code for the termination of transcription?
3
Based on the animation, put the following events of conjugation in order: Transfer of the DNA Fusion of the cell membranes Pulling of donor and recipient cells together
3, 2, 1
Ribosomes move along the mRNA in which direction?
5' to 3'
Which of the following is an example of a nucleoside analog?
5-bromouracil
Which of the following statements regarding RNA polymerase is true?
RNA polymerase reads the template strand of DNA. RNA polymerase adds nucleotides to the 3' end of the growing RNA molecule. RNA polymerase binds to the promoter region of the gene prior to starting RNA synthesis.
Hfr cells are associated with which of the following?
conjugation
What type of mutation can change all subsequent amino acids following it?
frameshift mutation
Ethidium bromide can result in _________________.
frameshift mutations via insertion or deletion of nucleotides.
All of the following are associated with the process of DNA replication
helicases primase DNA ligase
DNA synthesis occurs in which direction?
From 5' to 3' on both the leading and lagging strands.
Which of the following statements regarding operons is true?
-Inducible operons are transcribed only when they are activated. -Repressible operons are always transcribed unless they are deactivated by a repressor. -The structural genes of an operon typically have the same biochemical function in the cell.
What is the order of ribosomal sites that a charged tRNA molecule passes through?
A site, P site, E site
Which statement about conjugation is true?
After conjugation, each cell involved has a copy of the shared DNA.
Which of the following statements regarding the induction of the lac operon is true?
Allolactose serves as an inducer. The inducer acts by turning off the repressor. Induction of the operon ceases when lactose is absent from the system.
What is the role of DNA helicase in DNA replication?
DNA helicase uses the energy from ATP to break the hydrogen bonds between two DNA strands, thereby "unzipping" the molecule.
Which enzyme(s) can synthesize new strands of DNA?
DNA polymerase
The process of copying DNA prior to cell replication is known as _____________.
DNA replication.
Which of the following steps of transcription is INCORRECTLY paired with its function?
Elongation: RNA polymerase synthesizes a transcript on both strands of DNA to create multiple copies.
Which of the following statements concerning genetic mutations is FALSE?
Gene mutations always result in problems for cells and organisms.
What is a potential source of mutations from ionizing radiation?
Ions and free radicals resulting from ionizing radiation can break chromosomes.
What is the role of tryptophan in the trp operon?
It activates the repressor proteins.
How does the DNA polymerase know which nucleotide triphosphate to add to the growing strand?
It hydrogen-bonds the nucleotide to the parental strand, pairing adenines to thymines and guanines to cytosines.
When is the regulatory gene transcribed?
It is always transcribed.
Based on the animation, what is unique about the DNA transferred between two cells during conjugation?
It is transferred as a single strand.
Why is primase essential for DNA replication?
It provides a 3' end of the newly synthesized strand, allowing DNA polymerase to begin copying DNA.
Which of the following is NOT a characteristic of the genetic code?
More than one amino acid is associated with each codon.
Which of the following features of nuclear DNA lends support to the endosymbiotic theory?
Nuclear DNA is wrapped around histones. Nuclear DNA is linear.
Which of the following is NOT a characteristic of eukaryotic transcription?
Prokaryotic cells have three types of RNA polymerase. Eukaryotic cells have three types of RNA polymerase.
Which of the following happens to initiate specialized phage transduction?
Prophage integrates into the host genome AND bacteriophage enters lysogeny.
How does protein-dependent termination differ from protein-independent termination?
Protein-dependent termination involves the use of a protein to end transcription.
Which of the following statements concerning DNA replication is true?
The leading strand of DNA replication requires only one RNA primer. The lagging strand of DNA replication requires multiple RNA primers.
The leading strand in DNA replication is characterized by all of the following features
The leading strand requires one RNA primer. DNA polymerase starts at the origin and follows helicase. Synthesis is continuous and moves in the 5' to 3' direction.
What is meant by semiconservative replication?
The new copies of DNA contain one original strand of DNA and one new strand of DNA.
What might happen if the cell does not have RNAse?
The newly made chromosome would consist of DNA and RNA molecules.
How can a mismatch repair enzyme detect which strand contains the correct DNA sequence?
The original strand will likely have a methyl group attached, while the newly mutated strand will not.
What must occur for an organism to pass its genetic information on to its offspring?
The parent must copy its own DNA and provide a copy to its offspring.
Why is E. coli considered the model of bacterial conjugation?
The process of conjugation is best characterized in E. coli.
Which of the following statements regarding the lac operon is true?
The repressor proteins bind to the operator, preventing RNA polymerase from transcribing the structural genes.
Why is the transcription of structural genes of the trp operon turned off in the presence of tryptophan?
The structural genes are used to make tryptophan, which would not be needed if tryptophan is available.
Which of the following statements is false regarding the trp operon?
The structural genes of the trp operon are transcribed only in the presence of tryptophan.
Which of the following statements regarding the trp operon is true?
The trp operon is always activated unless deactivated by a repressor.
Which of the following statements regarding Okazaki fragments are true?
They are typically 1000 nucleotides in length. They are found on the lagging strand of DNA replication.
What is the function of stabilizing proteins?
They hold the separated strands apart and prevent their degredation.
What is the function of the connector proteins?
They link the leading strand DNA polymerase and the lagging strand DNA polymerase together.
Ethidium bromide is an example of which of the following?
a frameshift mutagen
The replication fork moves ___________.
ahead of the newly synthesized DNA.
Which of the following codes for leucine?
all of the above
According to the animation, where does the activation and repression of an operon occur?
at the operator region
Plasmids are extra chromosomal pieces of circular DNA that contain all of the following information
bacteriocins to kill bacterial competitors virulence factors that allow a bacterium to become pathogenic fertility factors for conjugation resistance factors for resistance to drugs and heavy metals
Release factors _________________________.
bind to the A site AND are coded by stop codons.
What serves as the template for DNA replication?
each of the original DNA strands
Which of the repair mechanism(s) requires assistance from DNA polymerase to make the correction?
excision-repair mechanism AND mismatch-repair mechanism
Enzymes known as photolyases are involved in which type of repair?
light-repair mechanism
Which of the following repair mechanism(s) does not involve the removal of nucleotides?
light-repair mechanism
Which of the following repair mechanisms might be involved in repairing a mutation that results from exposure to UV light?
light-repair mechanism AND excision-repair mechanism
Which of the following is not a part of the initiation complex?
mRNA
Which of the following is the copy of a DNA sequence used to make protein?
mRNA
Which of the following is a product of transcription?
mRNA, rRNA, tRNA
AUG codes for _________________.
methionine
All of the following regulatory RNAs are correctly described
microRNAs bind to messenger RNA to silence the message
A chemical that can increase the rate of mutations is called a _______________________.
mutagen.
Generalized transduction is initiated by ___________.
the lytic cycle of viral replication
Which of the following is the regulatory sequence responsible for control of an operon?
the operator
What is the target of the activated repressor protein?
the operator region of the operon
Which of the following is packaged by the bacteriophage during
the phage DNA with some of the host DNA
Translation is _________________________.
the process of making DNA from RNA.
Which genetic element codes for the repressor protein?
the regulatory gene
Which of the following would be an example of horizontal gene transfer?
the transfer of DNA from one bacterium to another
Transduction is _____________________.
the transfer of bacterial DNA from one host to another via a bacteriophage.
The role of transcription is ___________________.
to copy the information stored in DNA into RNA.
What is the purpose of bacterial conjugation?
to transfer DNA between two living cells
Which of the following is NOT a type of horizontal gene transfer?
transcription
Which of the following processes is INCORRECTLY paired?
transformation: the spontaneous change of genetic information in a species that creates monsters
