Chapter 5 micro
Which of the following statements about plasmids is false? ANSWER: -If present, plasmids are always essential to cell survival. -Plasmids are nonchromosomal DNA segments found in bacteria and a number of eukaryotic cells. -Plasmids are commonly shared among cells by horizontal gene transfer mechanisms. -Molecular biologists often use plasmids to generate cell lines that make useful products for medical applications. -Plasmids are easily manipulated in the laboratory.
If present, plasmids are always essential to cell survival.
How would you be able to determine if the Tn5 transposon you put into a bacterium integrated into the host genome? ANSWER: -The cells would become longer due to the extra DNA in them. -If the Tn5 transposon integrated into the host genome, the cells would show resistance to the antibiotic kanamycin. -If the Tn5 transposon integrated into the host genome, the cells would not be able to take in any new tranposons. -The cells would grow at a faster rate than without the transposon.
If the Tn5 transposon integrated into the host genome, the cells would show resistance to the antibiotic kanamycin.
Choose the true statement(s) about stop codons. To be marked correct, you'll need to select all true statements, as there may be more than one correct answer. ANSWER: -There are several stop codons in the genetic code. -Stop codons are needed to terminate transcription. -All organisms use the stop codon AUG to terminate protein synthesis. -Under specific circumstances, stop codons may encode non-standard amino acids.
-There are several stop codons in the genetic code. -Under specific circumstances, stop codons may encode non-standard amino acids.
Which of the following is involved in bringing amino acids to the ribosomes? ANSWER: -tRNA -mRNA -mRNA, tRNA, and rRNA are all involved in transporting amino acids to the ribosomes. -rRNA
-tRNA
At which point does a recipient cell become an F+ cell? Fusion of the cell membranes Attachment of the sex pilus Transfer of the single stranded F factor Pulling of donor and recipient cells together Formation of the complementary strand of the F factor ANSWER: 4 5 1 3 2
5
During elongation, how is the RNA synthesized? ANSWER: 3' to 5' Right to left 5' to 3' Left to right
5' to 3'
The leading strand of DNA is synthesized in which direction? ANSWER: 5' to 3' in the opposite direction as helix unwinding 5' to 3' in the same direction as helix unwinding 3' to 5'in the opposite direction of helix unwinding 3' to 5'in the same direction as helix unwinding
5' to 3' in the same direction as helix unwinding
Which direction are phosphodiester bonds of DNA usually built in? ANSWER: 3' → 5' 1' → 5' 5' → 3' 5' → 1' Any direction is fine and will not affect the function of the DNA strand.
5' → 3'
Based on the animation, what is transferred during bacterial conjugation? ANSWER: A conjugation pilus RNA A bacterial plasmid A bacterial chromosome
A bacterial plasmid
Which of the following statements is true about specialized transduction? ANSWER: -Specialized transduction occurs in all bacteriophage except the temperate phages. -Specialized transduction always directs the production of new phage particles immediately upon infecting the host bacterium. -Specialized transduction requires that bacteriophage infect at least two different cells to be carried out. -A bacteriophage may at some point become reactivated, excise itself and surrounding bacterial genes from the genome, and begin to build new phage particles. -Bacteriophage undergoing specialized transduction integrate their DNA into a random region of the host cell's genome.
A bacteriophage may at some point become reactivated, excise itself and surrounding bacterial genes from the genome, and begin to build new phage particles.
Which of the following events occurs during transcription? ANSWER: -mRNA binds to a ribosome in the cytoplasm. -A molecule of RNA is formed based on the sequence of nucleotides in DNA. -Those segments of the RNA strand that do not actually code for the protein are removed. -A cap is added to the RNA molecule. -The message in mRNA is translated into a protein.
A molecule of RNA is formed based on the sequence of nucleotides in DNA.
In the Ames test, what happens when his- bacteria are exposed to a chemical and experience a higher level of growth than the control? ANSWER: -The reversion rate is lower than seen for spontaneous mutations. -The his- bacteria now utilized histidine from the media. -The his- bacteria utilized DNA repair tools to fix the mutation. -A reversion mutation allowed the his- bacteria to regain their ability to make histidine (revert to his+). -The tested chemical is regarded as a non-mutagen.
A reversion mutation allowed the his- bacteria to regain their ability to make histidine (revert to his+).
What is the inducer molecule in the lac operon? ANSWER: Galactose Repressor proteins Lactose Glucose Allolactose
Allolactose
What is the key difference between donor cells and recipient cells? ANSWER: Size An F plasmid Cell membranes A chromosome
An F plasmid
Bacterial conjugation is often referred to as bacterial sex. Why is this term inaccurate? ANSWER: -Conjugation does not result in the formation of new offspring. -It does not require two cells to occur. -Bacteria are neither male nor female. -Sex is a phenomenon only seen in animals.
Conjugation does not result in the formation of new offspring.
Which statement about conjugation is false? ANSWER: -After conjugation, each cell involved has a copy of the shared DNA. -E. coli is the model for bacterial conjugation. -Conjugation is a process of bacterial reproduction.
Conjugation is a process of bacterial reproduction.
Which of the following statements about conjugation is false? ANSWER: -In conjugation a bacterium attaches to a neighboring bacterial cell that lacks a fertility plasmid. -In conjugation a bacterium carries a fertility plasmid. -Conjugation is sexual reproduction for bacteria. -In conjugation a bacterium forms a small hollow tube called a pilus. -Conjugation can be a problem because fertility plasmids often carry genes that endow cells with drug resistance or the ability to produce toxins.
Conjugation is sexual reproduction for bacteria.
Which of the following is NOT used by bacteria to acquire new genetic material? ANSWER: transformation conjugation crossing over transduction
Crossing over
Which one of the following does not play a role in translation? ANSWER: tRNA DNA Amino acids Ribosomes Anticodon
DNA
What characteristic of DNA allows two connected DNA polymerases to synthesize both the leading and lagging strands? ANSWER: DNA is flexible. DNA is double-stranded. DNA is antiparallel. DNA has a helical shape.
DNA is flexible.
Which statement about DNA replication is FALSE? ANSWER: -DNA polymerase builds a new strand by adding DNA nucleotides one at a time. -The two strands of parental DNA are separated during DNA replication. -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 ligase adds nucleotides to the lagging strand.
DNA ligase adds nucleotides to the lagging strand.
The molecule that seals the gaps between the pieces of DNA in the lagging strand is ANSWER: the replication fork. DNA ligase. DNA polymerase. RNA. the leading strand.
DNA ligase.
Which of the following is an example of a spontaneous mutation? ANSWER: -Yeast DNA is exposed to acridine dye, resulting in distortion of the DNA double helix. -DNA polymerase III accidently mismatches a G to a T during Escherichia coli DNA replication, resulting in a silent mutation. -Human cells are exposed to X-rays for a prolonged period of time, leading to multiple DNA strand breaks. -Plasmodium vivax cells are exposed to ultraviolet radiation, leading to the formation of thymine dimers within the DNA sequence.
DNA polymerase III accidently mismatches a G to a T during Escherichia coli DNA replication, resulting in a silent mutation.
Choose the true statement about prokaryotic and eukaryotic DNA replication. ANSWER: -Prokaryotic DNA polymerases replicate DNA 5' to 3', while eukaryotic DNA polymerases replicate DNA 3' to 5'. -Eukaryotic DNA replication involves less protein factors than does prokaryotic DNA replication. -Eukaryotic DNA replication begins at multiple origins of replication, while prokaryotic DNA replication begins at a single origin of replication. -Prokaryotic genomes take longer to replicate than eukaryotic genomes.
Eukaryotic DNA replication begins at multiple origins of replication, while prokaryotic DNA replication begins at a single origin of replication.
What is required by an F- cell to become an F+ cell? ANSWER: F+ chromosome F plasmid Conjugation pilus An F- cell to be a recipient
F plasmid
DNA transposons rely on the enzyme reverse transcriptase to insert a copy of cDNA into a new location in the genome. ANSWER: True False
False
Put the following enzymes in the order they participate in the DNA replication, from beginning to end. - Single-strand binding proteins - DNA polymerase III - Helicase - Primase ANSWER: -Single-strand binding proteins, Primase, DNA polymerase III, Helicase -Helicase, Single-strand binding proteins, primase, DNA polymerase III -Primase, Helicase, Single-strand binding proteins, DNA polymerase III -Helicase, DNA polymerase III, Single-strand DNA binding proteins, Primase
Helicase, Single-strand binding proteins, primase, DNA polymerase III
How would one increase the concentration of a particular polypeptide in a cell? ANSWER: Increase the amount of DNA Increase the level of transcription Increase the concentration of promoters
Increase the level of transcription
Which operons are never transcribed unless activated? ANSWER: Inducible operons Repressible operons Inducible and repressible operons
Inducible operons
Which of the following terms is correctly matched with its description? ANSWER: -Insertion mutations: Occur when a cell adds one or more nucleotides to its genome sequence. -Substitution mutations: Occur when an incorrect fatty acid is added. -Point mutations: Occur when an incorrect carbohydrate is added. -Deletion mutations: Occur when one or more amino acids are removed from a protein sequence. -Substitution mutations: Occur when an incorrect amino acid is added.
Insertion mutations: Occur when a cell adds one or more nucleotides to its genome sequence.
When is the repressor protein transcribed? ANSWER: -Only in the absence of tryptophan -It is always transcribed. -Only in the presence of tryptophan
It is always transcribed.
Why does a complex transposon often contain an extra piece of DNA between the two insertion elements? ANSWER: -It is often a gene that confers a survival advantage to the host, such as antibiotic resistance. -It prevents degradation of the whole transposon. -The insertion elements require a certain distance between them to function properly.
It is often a gene that confers a survival advantage to the host, such as antibiotic resistance.
What is the function of the conjugation pilus? ANSWER: It pulls the F+ and F- cells together. It carries the chromosome of F- cells. It contains an F plasmid. It converts F- cells into F+ cells.
It pulls the F+ and F- cells together.
What is the purpose of an anticodon? ANSWER: -It's a region on an rRNA that binds to a complementary codon on tRNA to ensure the proper amino acid is added to a growing protein. -It's a region on a tRNA that binds to a complementary codon on mRNA to ensure the proper amino acid is added to a growing protein. -It's a region on a DNA that binds to a complementary codon on mRNA to ensure the proper amino acid is added to a growing protein. -It's a region on an mRNA that binds to a complementary codon on rRNA to ensure the proper amino acid is added to a growing protein.
It's a region on a tRNA that binds to a complementary codon on mRNA to ensure the proper amino acid is added to a growing protein.
Which of the following are terms associated with Okazaki fragments? ANSWER: DNA ligase Lagging strand, DNA ligase, and discontinuous Lagging strand Discontinuous
Lagging strand, DNA ligase, and discontinuous
Which DNA strand is synthesized continuously? ANSWER: The leading and lagging strands are both synthesized continuously. Lagging strand Leading strand Neither the leading nor the lagging strand is synthesized continuously.
Leading strand
Which of the following repair mechanism(s) does not involve DNA polymerase? ANSWER: Light-repair mechanism Excision-repair mechanism Mismatch-repair mechanism
Light-repair mechanism
What are the components of a nucleotide? To be marked correct, you'll need to select all applicable components, as there may be more than one correct answer. ANSWER: Nitrogen base A sugar Phosphate Histones
Nitrogen base A sugar Phosphate
What cellular macromolecule is the fertility factor comprised of? ANSWER: Protein Nucleic acid Lipid Carbohydrate
Nucleic acid
Which of the following is a valid difference between the leading and lagging strands in DNA replication? ANSWER: -Helicase opens the leading strand of DNA at a faster rate than the lagging strand of DNA. -Following DNA replication, RNA primers are fully removed by the enzyme DNA ligase. -On the leading strand, only a single RNA primer is needed to initiate continuous DNA synthesis. -On the leading strand, DNA polymerase III replicates DNA from 5' to 3', whereas on the lagging strand DNA polymerase I builds DNA from 3' to 5'.
On the leading strand, only a single RNA primer is needed to initiate continuous DNA synthesis.
What is considered to be the average natural mutation rate that occurs during DNA replication? ANSWER: One in every trillion nucleotides replicated. One in every million nucleotides replicated. One in every billion nucleotides replicated. One in every ten thousand nucleotides replicated.
One in every billion nucleotides replicated.
How frequently do silent mutations occur? ANSWER: One out of every billion mutations One out of every three mutations Half of all mutations One out of every million mutations
One out of every three mutations
RNA differs from DNA in all of the following ways except ANSWER: RNA has directionality. RNA is single stranded. there are several different types of RNA including mRNA, tRNA, and rRNA. RNA has a hydroxyl group on the 2' carbon. in RNA, uracil (U) replaces thymine (T).
RNA has directionality.
According to the animation, which of the following makes mRNA from the information stored in a DNA template? ANSWER: RNA polymerase tRNA Ribosomes DNA polymerase
RNA polymerase
Which of the following is not an enzyme involved in DNA replication? ANSWER: RNA polymerase Helicase DNA polymerase III Primase
RNA polymerase
When the cell is NOT in the presence of tryptophan, ANSWER: -structural genes are not transcribed. -the repressor proteins bind to the operator. -the repressor proteins are active. -RNA polymerase can transcribe mRNA.
RNA polymerase can transcribe mRNA.
What type of pre-transcriptional regulation is the most likely to turn off the production of a substance that is already plentiful? ANSWER: Repressible operons Riboswitches Small, noncoding mRNAs Inducible operons
Repressible operons
Which operons are always transcribed unless deactivated? ANSWER: Inducible operons Repressible operons Inducible and repressible operons
Repressible operons
Choose the true statement about protein synthesis. ANSWER: -In eukaryotes, polysomes can develop before transcription finishes, whereas prokaryotic mRNA must first undergo processing. -In eukaryotes, translation occurs in the nucleus; in prokaryotes, translation occurs in the cytoplasm. -Prokaryotic cells produce polycistronic mRNA as a product of transcription, which must then be spliced to remove introns prior to translation. -The first amino acid in a eukaryotic protein sequence is methionine, whereas the first amino acid in a prokaryotic protein sequence is formyl methionine.
The first amino acid in a eukaryotic protein sequence is methionine, whereas the first amino acid in a prokaryotic protein sequence is formyl methionine.
Choose the true statement about the genetic code. ANSWER: -The genetic code varies widely among organisms, with each having a different set of codons for a corresponding amino acid. -The genetic code encodes 64 amino acids, one for each of the 64 corresponding codons. -A cell's mRNA code is read four nucleotides at a time to specify a single amino acid. -The genetic code is redundant, with multiple codons specifying a single amino acid.
The genetic code is redundant, with multiple codons specifying a single amino acid.
Which statement about DNA replication is CORRECT? ANSWER: -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 one of the strands of parental DNA. -The lagging strand is built continuously. -DNA ligase helps assemble the leading strand.
The leading strand is built continuously, and the lagging strand is built in pieces.
Why is light required for photolyases? ANSWER: -The light helps identify the damaged strands. -Light is used to activate the DNA polymerase to repair the gap. -Light excises the section of DNA to be repaired. -The light provides the energy to break the bonds between the thymine dimers.
The light provides the energy to break the bonds between the thymine dimers.
Which of the following is an example of horizontal gene transfer in bacteria? ANSWER: -Transformation -Transduction -Conjugation and transformation -Conjugation -Transduction, conjugation, and transformation
Transduction, conjugation, and transformation
What is the hallmark of all horizontal gene transfers? ANSWER: -Transfer of DNA using a virus -Transfer of DNA from parent to offspring -The use of plasmids -Transfer of DNA between organisms of the same generation
Transfer of DNA between organisms of the same generation
How does transformation differ from conjugation? ANSWER: Transformation involves a pilus. Transformation takes up DNA from the environment. Transformation requires DNA to be on a plasmid. Transformation requires only fresh DNA be used. Transformation can only exchange DNA between bacteria of the same species.
Transformation takes up DNA from the environment.
An organism's genotype influences its phenotype. ANSWER: True False
True
DNA replication is a semiconservative process. ANSWER: True False
True
Many mutagens cause a rate of mutation that promotes the development of cancers; such mutagens are called carcinogens. ANSWER: True False
True
Why is the tryptophan operon turned off in the presence of tryptophan? ANSWER: -Tryptophan binds to and activates the repressor proteins; the repressor proteins, in turn, bind to the operator, preventing transcription. -Tryptophan is not an important amino acid for cells. -Tryptophan can be used over and over again in the cell.
Tryptophan binds to and activates the repressor proteins; the repressor proteins, in turn, bind to the operator, preventing transcription.
Competent cells are cells that ANSWER: -are killed by heat. -have the ability to produce capsules. -are also considered "rough-strain" based on colony phenotype. -can take up DNA from their surrounding environment and integrate it into their own chromosomes by recombination.
can take up DNA from their surrounding environment and integrate it into their own chromosomes by recombination.
Which of the following is not directly involved in protein synthesis? ANSWER: rRNA tRNA dsRNA mRNA
dsRNA
A base insertion or deletion in the translated region of the gene may lead to ANSWER: missense mutation. nonsense mutation. frameshift mutation. silent mutation.
frameshift mutation.
Which of the following terms refers to the genetic makeup of an organism? ANSWER: purine genotype primosome heritable phenotype
genotype
DNA replication is ANSWER: the process a cell uses to make protein. slow. the exact same for prokaryotes and eukaryotes. error prone. going to result in relatively few mutations.
going to result in relatively few mutations.
Ribosomes contain which of the following? ANSWER: mRNA, tRNA, and rRNA are all found as part of the ribosome. tRNA rRNA mRNA
rRNA
Key mechanisms of horizontal gene transfer include all of the following except ANSWER: transposons. reproduction. transformation. conjugation. transduction.
reproduction.
The site of translation is ANSWER: -the cell nucleus. -the Golgi apparatus. -the plasma membrane. -ribosomes in the cell nucleus. -ribosomes in the cell cytoplasm
ribosomes in the cell cytoplasm.
A ________ mutation does not change the amino acid sequence of a protein. ANSWER: missense nonsense silent frameshift deletion
silent
A mutation that affects the genotype of the organism but not the phenotype is called a ANSWER: missense mutation. nonsense mutation. frameshift mutation. silent mutation.
silent mutation.
Naturally occurring mutations are often referred to as ________ mutations. ANSWER: deleterious unnoticed spontaneous insertion neutral
spontaneous
RNA that has hydrogen bonded to itself forms a ANSWER: stem loop. termination protein. terminator sequence. promoter sequence.
stem loop.
Frameshift mutations can do all of the following except ANSWER: -render the protein useless to the cell. -insert or eliminate an amino acid. -substitute one amino acid for another. -insert or delete a DNA base. change the protein's amino acid sequence.
substitute one amino acid for another.
Sickle cell anemia is a genetic disorder that causes red blood cells to take on an abnormal, crescent shape. This inherited disorder is the result of a single base change from A to T. This changes the amino acid glutamic acid to valine at position six of the hemoglobin protein. Based on this information, sickle cell anemia results from a(n) ________ mutation. ANSWER: insertion mutation deletion mutation substitution mutation silent mutation
substitution mutation
RNA polymerase is guided by the ANSWER: template strand of DNA. RNA strand. coding strand of DNA.
template strand of DNA.
When the cell is not in the presence of lactose, ANSWER: -the repressor proteins bind to the operator. -the repressor proteins are inactivated. -transcription of the structural genes occurs. -no transcription of the regulatory genes occurs
the repressor proteins bind to the operator.
RNA is distinguished from DNA because only RNA: ANSWER: typically exists as a single-stranded molecule. has a 3' to 5' directionality. is composed of nucleotides that contain the nitrogen bases T, C, G, and A. is composed of nucleotides that contain the sugar deoxyribose.
typically exists as a single-stranded molecule.
Helicase ANSWER: unwinds the DNA. causes a bubble of single-stranded DNA to form. creates the replication fork. allows for DNA polymerase III to bind to the DNA. relieves coiling tension that develops as the helix is unwound.
unwinds the DNA.
Which of the following nitrogen bases is found only in RNA and NOT in DNA? ANSWER: thymine uracil adenine cytosine guanine
uracil
Which of the following is the correct mRNA sequence encoded by the DNA sequence: TAC GGT CAC TTC ACT? ANSWER: UAC GGU CAC UUC ACU AUG CCA GUG AAG UGA GCA UUG ACA GGA GUC ATG CCA GTG AAG TGA
AUG CCA GUG AAG UGA
Which of the following contributes to DNA replication accuracy? To be marked correct, you'll need to select all true statements, as there may be more than one correct answer. ANSWER: -DNA replication accuracy is improved thanks to complementary base pairing rules. -A slow rate of DNA replication contributes to accuracy. -The capacity to proofread improves DNA replication accuracy. -The use of primase improves DNA replication accuracy.
-DNA replication accuracy is improved thanks to complementary base pairing rules. -The capacity to proofread improves DNA replication accuracy.
Place the following events in the correct order as they occur on the lagging strand: 1. Helix unwinding 2. DNA polymerase III builds DNA 3. DNA polymerase I acts 4. Ligase glues Okazaki fragments together 5. RNA primase builds RNA primers
1, 5, 2, 3, 4
As replication proceeds in a prokaryotic cell, how many replication forks exist on one chromosome? ANSWER: 1 2 3 4 5
2
Put the following steps of protein synthesis in the order that they occur in a eukaryotic cell: Translation ends at a stop codon RNA polymerase transcribes mRNA from DNA Protein sequence is elongated Translation initiates mRNA is processed and travels to a ribosome ANSWER: 4, 3, 2, 5, 1 5, 2, 4, 1, 3 2, 4, 3, 5, 1 2, 5, 4, 3, 1
2, 5, 4, 3, 1
At what site on the chromosome does DNA replication begin? ANSWER: On the daughter strand At the replication fork At the origin of replication At the primosome
At the origin of replication
Which of the following is not a mechanism for horizontal gene transfer? ANSWER: Binary fission Conjugation Transduction Transformation
Binary fission
What is the function of single-strand binding proteins? ANSWER: Bind to the DNA strands and create RNA primers to jumpstart replication Bind to the DNA strands to glue Okazaki fragments together Bind to the DNA strands and unwind them, creating a replication fork Bind to the DNA strands near the replication fork to keep them separated
Bind to the DNA strands near the replication fork to keep them separated
________ mutagens are agents that can introduce genetic change through recombination. ANSWER: Biological Organic Frameshift Physical Chemical
Biological
Which of the following build(s) new strands of DNA? ANSWER: The leading strand Parental DNA The origins of replication The lagging strand DNA polymerases
DNA polymerases
The primary flow of genetic information in cells is from ANSWER: protein → RNA → DNA. DNA → RNA → protein. protein → DNA → RNA. DNA → protein → RNA. RNA → protein → DNA.
DNA → RNA → protein.
Which of the following repair enzymes cannot repair thymine dimers? ANSWER: Light-repair enzymes Mismatch-repair enzymes Excision-repair enzymes
Mismatch-repair enzymes
Which of the following statements about mutations is false? ANSWER: -Mutations are essential to evolution within species. -A mutation in a single-celled organism is more likely to be passed to daughter cells than a multicellular organism. -Multicellular organisms evolve faster than unicellular organisms. -A mutation is a change in the genetic material of a cell or virus. -Mutations are essential to variation within species.
Multicellular organisms evolve faster than unicellular organisms.
During DNA replication, which nucleotide will bind to an A nucleotide in the parental DNA? ANSWER: C A G T U
T
What must occur for bacterial conjugation to take place? ANSWER: -Each cell must contain a plasmid. -One of the cells must be E. coli. -The cells must come into contact with each other. -The cells must transfer RNA.
The cells must come into contact with each other.
How is DNA methylation used in DNA repair? ANSWER: -The mismatch-repair enzymes can use a lack of methylation to identify and remove newly synthesized DNA. -Methyl groups are required to cut DNA. -Methyl groups activate photolyases in light-repair. -Methyl groups identify thymine dimers in the DNA.
The mismatch-repair enzymes can use a lack of methylation to identify and remove newly synthesized DNA.
According to the animation, where on the DNA strand does a repressor bind? ANSWER: The structural genes The promoter The inducer The operator
The operator
With which genetic region does the repressor protein interact? ANSWER: The regulatory gene The operator region lacY The promoter region lacZ
The operator region
Which of the following statements about the primosome is false? ANSWER: -The primosome includes RNA polymerase to build the protein. -The primosome includes primase to lay down RNA primers that will jump-start replication. -The primosome includes helicase to unwind the DNA. -The primosome is responsible for starting DNA replication. -The primosome is recruited to the origin of replication.
The primosome includes RNA polymerase to build the protein.
What is the initial target of RNA polymerase? ANSWER: The promoter The template DNA The terminator region
The promoter
Which of the following genetic elements is transcribed into a single mRNA? ANSWER: The promoter The structural genes The operator The inducer The repressor
The structural genes
Why is the DNA synthesis of the lagging strand considered discontinuous? ANSWER: DNA synthesis on the lagging strand occurs 3' to 5'. The lagging strand only requires one primer instead of multiple primers. The synthesis is moving in the opposite direction from the replication fork. The lagging strand only produces single-stranded DNA molecules.
The synthesis is moving in the opposite direction from the replication fork.
Which of the following statements about thymine dimers is false? ANSWER: -They can be produced by exposure to UV light. -If resulting mutations accumulate, it can result in cancers. -Patients with xeroderma pigmentosum have faulty DNA repair mechanisms. -They are repaired by excision repair. -They are repaired by one enzyme that can clip out, lay down new nucleotides, and seal the gap.
They are repaired by one enzyme that can clip out, lay down new nucleotides, and seal the gap.
How is a complex transposon different from a simple transposon? ANSWER: -Complex transposons have one very long insertion sequence. -Complex transposons code for different types of transposase. -They have two simple transposons with another DNA sequence between them. -They always integrate in multiple copies into the host genome.
They have two simple transposons with another DNA sequence between them.
What is the function of the connector proteins? ANSWER: They allow DNA synthesis to occur in the 3' to 5' direction. They link the leading strand DNA polymerase and the lagging strand DNA polymerase together. They produce the Okazaki fragments. They enable one parental DNA strand and one newly synthesized DNA strand to be held together.
They link the leading strand DNA polymerase and the lagging strand DNA polymerase together.
What is the basic function of the lac operon? ANSWER: -To produce glucose when none is available -To code for enzymes involved in synthesizing lactose. -To produce lactose when none is present -To code for enzymes involved in catabolizing lactose.
To code for enzymes involved in catabolizing lactose.
What is the overall function of the trp operon? ANSWER: -To ensure that the cell has a supply of tryptophan at all times -To always make sure the operator is being bound to repressor proteins -To control the production of repressor proteins -To block RNA polymerase from the structural genes
To ensure that the cell has a supply of tryptophan at all times
Which of the following statements about an inducible operon is false? ANSWER: -When off, RNA polymerase is blocked by the operator. -When present, an inducer will inactivate the repressor. -When off, the repressor binds to the operator. -Certain conditions activate transcription. It is off by default.
When off, RNA polymerase is blocked by the operator.
Where can the DNA of prokaryotic cells be found? ANSWER: nucleus around histones nucleoid nucleolus in numerous linear chromosomes
nucleoid
Eukaryotic replication differs from prokaryotic replication, because prokaryotic replication ANSWER: -typically has more replication initiation sites. -takes longer to copy. -involves more protein factors. -involves only one circular chromosome. -has more DNA to copy.
involves only one circular chromosome.
A recombinant cell ANSWER: -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.
is a cell that receives DNA from an outside source and incorporates it into its own.
Which of the following can be translated into protein? ANSWER: rRNA mRNA mRNA, tRNA, and rRNA are all translated into protein. tRNA
mRNA
Which of the following does not occur during RNA processing? ANSWER: -Segments of the RNA strand that do not actually code for the protein are removed. -mRNA attaches to the small subunit of a ribosome. -Adenine nucleotides are added to the end of the RNA strand, forming a tail. -Segments of RNA that do code for the protein are reconnected. -A modified guanine nucleotide is added to the beginning of the RNA strand as a cap.
mRNA attaches to the small subunit of a ribosome.
Which of the following is a correct statement about mRNA? ANSWER: -mRNA moves from the nucleus to the cytoplasm following RNA processing. -Segments of mRNA that code for protein are removed before translation. -mRNA binds directly to amino acids during translation. -mRNA includes a cap that consists of extra adenine nucleotides. -mRNA is transcribed from DNA in the cytoplasm.
mRNA moves from the nucleus to the cytoplasm following RNA processing.
Transcription produces which of the following? ANSWER: -mRNA -rRNA -tRNA -mRNA and tRNA -mRNA and rRNA -mRNA, tRNA, and rRNA are all produced by transcription.
mRNA, tRNA, and rRNA are all produced by transcription.
A base substitution that changes a codon coding for an amino acid to a stop codon is called a ANSWER: silent mutation. nonsense mutation. missense mutation. frameshift mutation.
nonsense mutation.
