Practice Questions_dr. Schlegel_may_aug2011 _pt.2
Questions and Answers
- 1.
Binding of an autoinducer peptide to the sensor kinase of a quorum sensing system in a Gram-positive bacterium leads to altered regulation of genetic loci present on different parts of the chromosome and transcribed in different directions. Which of the following would best describe the organization of the genes targeted by this quorum-sensing system?
- A.
Divergent operons
- B.
Regulon
- C.
Contrary operons
- D.
Divergent regulation
- E.
Indirect regulation
Correct Answer
B. RegulonExplanation
The organization of the genes targeted by this quorum-sensing system is best described as a regulon. A regulon refers to a set of genes or operons that are controlled by a common regulatory protein or mechanism. In this case, the binding of the autoinducer peptide to the sensor kinase leads to altered regulation of genetic loci present on different parts of the chromosome and transcribed in different directions. This suggests that the quorum-sensing system is coordinating the expression of multiple genes or operons, which is characteristic of a regulon.Rate this question:
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- 2.
The SOS response is a DNA repair mechanism that responds to extreme DNA damage
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
The SOS response is a DNA repair mechanism that is activated in response to extreme DNA damage. When the DNA is severely damaged, the SOS response is triggered to prevent further damage and promote DNA repair. This response involves the upregulation of various genes involved in DNA repair and replication, as well as the activation of error-prone DNA polymerases that can introduce mutations in order to bypass the damaged DNA. Overall, the SOS response is an important mechanism to ensure the survival of cells under conditions of extreme DNA damage.Rate this question:
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- 3.
Which 3 of the following could be required or produced by an organism using anaerobic respiration?
- A.
Organic acids
- B.
Cytochromes
- C.
Nitrite
- D.
Oxygen
- E.
Sulfate
Correct Answer(s)
B. Cytochromes
C. Nitrite
E. SulfateExplanation
Answer: B., C. and E. Organic acids are produced by fermentative pathways. Anaerobic respiration does not require oxygen as terminal electron acceptor—this function is taken by other molecules not derived from glycolysis (sulfate, nitrate, fumarate, ferric ion, etc). Anarobic respiration DOES require an ETC (hence cytochromes), an electron acceptor such as sulfate, and will produce a reduced form of that acceptor, such as nitrite.Rate this question:
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- 4.
In generalized transduction, viruses carry random DNA sequences from one cell to another
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Generalized transduction is a type of horizontal gene transfer where viruses, called bacteriophages, carry random fragments of host DNA from one bacterial cell to another. This occurs when a bacteriophage mistakenly packages host DNA instead of its own DNA during the viral replication process. As a result, when the virus infects another bacterial cell, it transfers this random DNA sequence, which can then be incorporated into the recipient cell's genome. Therefore, the statement that in generalized transduction, viruses carry random DNA sequences from one cell to another is true.Rate this question:
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- 5.
A(n) __________ is a specific sequence of nucleotides that codes for a protein or an RNA molecule.
- A.
Transposons
- B.
Gene
- C.
Competent
- D.
Missense
- E.
Anticodon
Correct Answer
B. GeneExplanation
A gene is a specific sequence of nucleotides that codes for a protein or an RNA molecule. It is the fundamental unit of heredity and carries the instructions for the synthesis of proteins, which are essential for the functioning and development of organisms. Genes are located on chromosomes and are responsible for the transmission of traits from parents to offspring. They play a crucial role in determining an individual's characteristics and are involved in various biological processes.Rate this question:
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- 6.
If the codon AUG, coding for methionine, were mutated to AAG, coding for lysine, this would be an example of a(n) __________ mutation.
- A.
Transposons
- B.
Gene
- C.
Competent
- D.
Missense
- E.
Anticodon
Correct Answer
D. MissenseExplanation
A missense mutation is a type of mutation where a single nucleotide change in the DNA sequence results in the substitution of one amino acid in the protein sequence for another. In this case, the codon AUG, which codes for methionine, is mutated to AAG, which codes for lysine. This change in the DNA sequence leads to the incorporation of lysine instead of methionine in the protein, resulting in a missense mutation.Rate this question:
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- 7.
The __________ of a transfer RNA molecule is complementary to a codon in a messenger RNA molecule.
- A.
Transposons
- B.
Gene
- C.
Competent
- D.
Missense
- E.
Anticodon
Correct Answer
E. AnticodonExplanation
The anticodon of a transfer RNA molecule is complementary to a codon in a messenger RNA molecule. The anticodon is a sequence of three nucleotides located on the tRNA molecule that specifically recognizes and binds to the corresponding codon on the mRNA during protein synthesis. This complementary base pairing between the anticodon and codon ensures that the correct amino acid is added to the growing polypeptide chain.Rate this question:
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- 8.
Cells that are able to perform transformation are said to be __________.
- A.
Transposons
- B.
Gene
- C.
Competent
- D.
Missense
- E.
Anticodon
Correct Answer
C. CompetentExplanation
Cells that are able to perform transformation are referred to as "competent". This term is commonly used in molecular biology to describe cells that have been treated or engineered to take up foreign DNA molecules and incorporate them into their own genetic material. Competent cells have enhanced abilities to uptake and express exogenous DNA, making them useful tools in genetic engineering and biotechnology applications.Rate this question:
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- 9.
"Jumping genes" that can move from one location to another in an organism's genome are called __________.
- A.
Transposons
- B.
Gene
- C.
Competent
- D.
Missense
- E.
Anticodon
Correct Answer
A. TransposonsExplanation
Transposons are "jumping genes" that have the ability to move from one location to another within an organism's genome. They are also known as transposable elements and can cause genetic changes by inserting themselves into different positions in the DNA sequence. This mobility allows transposons to play a role in evolution and can have both positive and negative effects on an organism's phenotype.Rate this question:
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- 10.
The OmpR response regulator is activated in the presence of high solutes. One of the genes activated by OmpR is micF, whose nucleic acid product binds the ompF message and ends up reducing OmpF protein production, thereby reducing solute uptake. Which of the following terms would best describe micF and the stage at which it regulates OmpF production?
- A.
An antiterminator, acts on transcription
- B.
A kinase, regulates post-translationally
- C.
An antisense RNA, alters translation
- D.
An RNA stabilizing protein, alters translation
- E.
Sigma factor, acts on transcription
Correct Answer
C. An antisense RNA, alters translationExplanation
The product of micF is a nucleic acid, so the most likely way it would bind to mRNA would be by sequence complementarity. The fact that it binds mRNA means that it is working AFTER transcription. Of the options presented, it would have to be an antisense RNA (also, all of the other options are proteins)Rate this question:
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- 11.
During translation, the growing polypeptide is positioned in the __________ of the ribosome
- A.
Promoters
- B.
Triphosphate deoxyribonucleotides
- C.
P site
- D.
Replication fork /bubble
- E.
Leading strand
Correct Answer
C. P siteExplanation
During translation, the growing polypeptide is positioned in the P site of the ribosome. The P site, also known as the peptidyl site, is one of the three binding sites on the ribosome where tRNA molecules are held during protein synthesis. The P site specifically holds the tRNA molecule carrying the growing polypeptide chain, allowing for the addition of new amino acids to the chain.Rate this question:
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- 12.
dATP and dCTP are examples of __________, the building blocks of DNA molecules
- A.
Promoters
- B.
Triphosphate deoxyribonucleotides
- C.
P site
- D.
Replication fork /bubble
- E.
Leading strand
Correct Answer
B. Triphosphate deoxyribonucleotidesExplanation
dATP and dCTP are examples of triphosphate deoxyribonucleotides, which are the building blocks of DNA molecules. These molecules are essential for DNA replication and synthesis, as they provide the necessary nucleotides to form the DNA chain. The "tri-" in triphosphate indicates that these molecules have three phosphate groups attached to the sugar backbone, providing energy for the DNA synthesis process. Deoxyribonucleotides refer to the type of sugar present in the molecule, which is deoxyribose. Therefore, dATP and dCTP are specific examples of triphosphate deoxyribonucleotides that contribute to the formation of DNA molecules.Rate this question:
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- 13.
The point at which a DNA double helix is "unzipped" is the __________.
- A.
Promoters
- B.
Triphosphate deoxyribonucleotides
- C.
P site
- D.
Replication fork /bubble
- E.
Leading strand
Correct Answer
D. Replication fork /bubbleExplanation
The replication fork/bubble is the point at which a DNA double helix is "unzipped" during the process of DNA replication. This is where the two strands of the DNA molecule separate and serve as templates for the synthesis of new complementary strands. The replication fork/bubble is formed by the action of enzymes called helicases, which unwind the DNA helix and create a Y-shaped structure. The replication fork/bubble is a crucial site for DNA replication as it allows for the simultaneous synthesis of both leading and lagging strands.Rate this question:
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- 14.
The __________ is the DNA strand that is synthesized continuously during DNA replication.
- A.
Promoters
- B.
Triphosphate deoxyribonucleotides
- C.
P site
- D.
Replication fork /bubble
- E.
Leading strand
Correct Answer
E. Leading strandExplanation
The leading strand is the DNA strand that is synthesized continuously during DNA replication. This is because the leading strand is oriented in the 3' to 5' direction, which allows DNA polymerase to add nucleotides in a continuous manner. In contrast, the lagging strand is oriented in the opposite direction (5' to 3') and requires the synthesis of short Okazaki fragments that are later joined together. Therefore, the leading strand is the correct answer as it is the strand that is synthesized continuously during DNA replication.Rate this question:
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- 15.
RNA polymerase initiates transcription by recognizing specific nucleotide sequences called __________. .
- A.
Promoters
- B.
Triphosphate deoxyribonucleotides
- C.
P site
- D.
Replication fork /bubble
- E.
Leading strand
Correct Answer
A. PromotersExplanation
RNA polymerase initiates transcription by recognizing specific nucleotide sequences called promoters. Promoters are regions of DNA that signal the starting point for transcription. They provide binding sites for RNA polymerase and other transcription factors, allowing the initiation of transcription and the synthesis of RNA from the DNA template strand.Rate this question:
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