GENETICS Flashcards
- Which enzyme is responsible for relaxing supercoiling in closed circular DNA?
A. DNA Helicase
B. DNA Gyrase (Type 2 Topoisomerase)
C. DNA Polymerase
D. Anabolic Polymerase
B. DNA Gyrase (Type 2 Topoisomerase)
Rationale: DNA Gyrase, also known as Type 2 Topoisomerase, alleviates supercoiling in closed circular DNA. DNA helicase unzips the DNA molecule, DNA polymerase helps in synthesis of the new strand, and anabolic polymerase isn’t a known enzyme in the DNA replication process.
- Which antibiotics target DNA Gyrase?
A. Penicillin
B. Quinolones
C. Tetracycline
D. Macrolides
B. Quinolones
Rationale: Quinolones and their derivatives, fluoroquinolones, specifically target and inhibit the function of DNA gyrase.
- In the central dogma of molecular biology, what does DNA specify?
A. The structure of lipids
B. The structure of carbohydrates
C. The structure of proteins and enzymes
D. The structure of RNA
C. The structure of proteins and enzymes
Rationale: The central dogma of molecular biology suggests that DNA contains the instructions that dictate the structure of proteins and enzymes, which in turn govern the cell’s functions.
- When does DNA replication occur in bacteria?
A. After the bacterium multiplies
B. Before the bacterium multiplies
C. During bacterial conjugation
D. When the bacterium is exposed to light
B. Before the bacterium multiplies
Rationale: DNA replication must occur before a bacterium multiplies to ensure that both daughter cells receive an identical copy of the genome.
- Which enzyme is responsible for unwinding the DNA molecule during replication?
A. DNA Polymerase
B. DNA Gyrase
C. DNA Helicase
D. RNA Polymerase
C. DNA Helicase
Rationale: DNA helicase is the enzyme that unwinds the DNA molecule by breaking hydrogen bonds between the complementary nucleotide bases during replication.
- Which strand is synthesized continuously during DNA replication?
A. Template strand
B. Leading strand
C. Lagging strand
D. Antiparallel strand
B. Leading strand
Rationale: The leading strand is synthesized continuously as a single long chain of nucleotides in the 5’ to 3’ direction during DNA replication.
- What are the short fragments synthesized on the lagging strand called?
A. Polypeptides
B. Ribonucleotides
C. Okazaki fragments
D. Helicase fragments
C. Okazaki fragments
Rationale: The lagging strand is synthesized discontinuously in short segments known as Okazaki fragments.
- Which enzyme uses the parent strand as a guide during replication?
A. DNA Helicase
B. RNA Polymerase
C. DNA Gyrase
D. DNA Polymerase
D. DNA Polymerase
Rationale: DNA polymerase is the enzyme that synthesizes the new DNA strand using the parent strand as a guide to ensure the correct sequence is maintained.
- DNA replication in bacteria begins at which site?
A. Replication terminus
B. Replication fork
C. Origin of replication (oRIC)
D. Polymerase chain reaction site
C. Origin of replication (oRIC)
Rationale: DNA replication in bacteria initiates at a specific site known as the origin of replication (oRIC).
- In which direction is the new DNA strand synthesized?
A. 3’ to 5’
B. 5’ to 3’
C. 5’ to 5’
D. 3’ to 3’
B. 5’ to 3’
Rationale: DNA synthesis always proceeds in the 5’ to 3’ direction. This refers to the new strand being synthesized, regardless of whether it’s the leading or lagging strand.
- Which enzyme is primarily responsible for adding nucleotides during DNA replication?
A. DNA Pol I
B. DNA Pol II
C. DNA Pol III
D. DNA Ligase
C. DNA Pol III
Rationale: DNA Pol III is the main replicative enzyme, responsible for incorporating nucleotides into the growing DNA strand during replication.
- Which enzyme connects Okazaki fragments to create a continuous DNA strand?
A. Primase
B. Helicase
C. DNA Gyrase
D. Ligase
D. Ligase
Rationale: DNA Ligase functions to seal gaps between Okazaki fragments on the lagging strand, ensuring a continuous DNA strand.
- Which enzyme requires an RNA primer to initiate DNA synthesis?
A. RNA Polymerase
B. DNA Polymerase
C. DNA Gyrase
D. Helicase
B. DNA Polymerase
Rationale: DNA Polymerase requires an RNA primer to start DNA synthesis, whereas RNA Polymerase can start RNA synthesis without a primer.
- What role does DNA Pol I play in DNA replication?
A. Repair
B. Adding nucleotides
C. Proofreading
D. Unwinding DNA
C. Proofreading
Rationale: DNA Pol I possesses proofreading capabilities, ensuring that the DNA sequence is correctly replicated with high fidelity.
- Which enzyme initiates the unwinding of DNA during replication?
A. DNA Pol II
B. Helicase
C. Ligase
D. Primase
B. Helicase
Rationale: Helicase is the enzyme responsible for unwinding the DNA, initiating the process at the oRIC during DNA replication.
- The activity of which enzyme introduces supercoils into the DNA ahead of the replication fork?
A. Primase
B. DNA Gyrase
C. Helicase
D. DNA Pol I
C. Helicase
Rationale: The unwinding action of helicase introduces supercoils into the DNA ahead of the replication fork, necessitating the action of DNA Gyrase to counteract these supercoils.
- Which enzyme relieves the supercoils formed during DNA replication?
A. Primase
B. Helicase
C. DNA Gyrase
D. DNA Pol III
C. DNA Gyrase
Rationale: DNA Gyrase, also known as Topoisomerase 2, functions to relieve supercoils that form in DNA due to the activity of helicase during replication.
- Which enzyme synthesizes RNA primers during DNA replication?
A. DNA Pol III
B. DNA Ligase
C. Primase
D. Helicase
C. Primase
Rationale: Primase is responsible for synthesizing RNA primers, which provide the necessary starting point for DNA Pol III during DNA replication.
- Which enzyme is involved in DNA repair mechanisms?
A. DNA Pol I
B. DNA Pol II
C. DNA Pol III
D. Primase
B. DNA Pol II
Rationale: DNA Pol II plays a key role in DNA repair mechanisms, ensuring the integrity of the genetic information.
- Which direction does DNA replication proceed in?
A. Bidirectional
B. Unidirectional from 5’ to 3’
C. Unidirectional from 3’ to 5’
D. Random
A. Bidirectional
Rationale: DNA replication is bidirectional, meaning it proceeds in two opposite directions from the origin of replication (oRIC). This ensures efficient replication of the entire DNA molecule.
- Where does DNA transcription occur in bacteria?
A. Mitochondria
B. Nucleoid region
C. Endoplasmic reticulum
D. Nucleus
B. Nucleoid region
Rationale: In bacteria, DNA transcription takes place in the nucleoid region of the cytoplasm, as bacteria lack a membrane-bound nucleus.
- Which enzyme binds complementary RNA nucleotides to DNA during transcription?
A. DNA Polymerase
B. Helicase
C. RNA Polymerase
D. Ligase
C. RNA Polymerase
Rationale: RNA Polymerase is the enzyme responsible for linking RNA nucleotides that are complementary to the genetic sequences in DNA during transcription.
- What is the role of the promoter region in transcription?
A. It marks the end of transcription.
B. It aids in RNA splicing.
C. It is where RNA polymerase binds to initiate transcription.
D. It aids in translation.
C. It is where RNA polymerase binds to initiate transcription.
Rationale: The promoter region of the DNA is recognized by RNA polymerase and signals the beginning of transcription.
- Which protein assists in terminating transcription in bacteria?
A. Ribosome
B. Helicase
C. Rho protein
D. DNA polymerase
C. Rho protein
Rationale: The Rho protein aids in the termination of transcription, ensuring the process ends at the correct nucleotide sequence.
- Which process uses ribosomes to interpret nucleotide sequences and produce polypeptides?
A. Transcription
B. Replication
C. Translation
D. Mutation
C. Translation
Rationale: Translation is the mechanism in which ribosomes read nucleotide sequences to synthesize polypeptides composed of specific amino acid sequences.
- What amino acid marks the start of translation?
A. Glycine
B. Tryptophan
C. Methionine
D. Phenylalanine
C. Methionine
Rationale: Translation always begins with the amino acid methionine, which corresponds to the nucleotide sequence AUG.
- Which sequence marks the end of transcription?
A. Codon sequence
B. Promoter region
C. Terminator sequence
D. Exon sequence
C. Terminator sequence
Rationale: The terminator sequence in DNA indicates the endpoint of transcription, signaling RNA polymerase to release the transcribed RNA.
- During which phase of transcription is the RNA strand elongated?
A. Initiation
B. Elongation
C. Termination
D. Translation
B. Elongation
Rationale: The elongation phase of transcription involves the addition of RNA nucleotides to the growing strand, extending its length.
- How is genetic information transferred from DNA to RNA?
A. Replication
B. Translation
C. Transcription
D. Mutation
C. Transcription
Rationale: Transcription is the process through which the genetic code from DNA is transferred to RNA, effectively converting DNA sequences into RNA sequences.
- Which nucleotide sequence corresponds to the amino acid methionine in translation?
A. UGA
B. UUU
C. AUG
D. GUA
C. AUG
Rationale: In translation, the amino acid methionine is coded for by the nucleotide sequence AUG, signaling the start of the protein synthesis process.
- What type of mutation involves the replacement of one nucleotide with another in the DNA sequence?
A. Addition
B. Deletion
C. Substitution
D. Frameshift
C. Substitution
Rationale: A substitution mutation involves replacing one nucleotide with another in the DNA sequence, without adding or removing any nucleotides.
- In which mutation is an amino acid replaced with a different amino acid due to a single nucleotide change?
A. Missense Mutation
B. Nonsense Mutation
C. Silent Mutation
D. Frameshift Mutation
A. Missense Mutation
Rationale: A missense mutation results from a single nucleotide change that leads to the replacement of one amino acid with another in the resultant protein.
- Which mutation results in the premature termination of protein synthesis?
A. Missense Mutation
B. Silent Mutation
C. Nonsense Mutation
D. Transition
C. Nonsense Mutation
Rationale: A nonsense mutation changes an amino acid codon into a stop codon, leading to the premature termination of the protein synthesis.
- Which mutation has no effect on the amino acid sequence of the resultant protein?
A. Nonsense Mutation
B. Missense Mutation
C. Silent Mutation
D. Frameshift Mutation
C. Silent Mutation
Rationale: Silent mutations result in no change to the amino acid sequence of the resulting protein despite the base change.
- What occurs in a frameshift mutation?
A. Replacement of one nucleotide
B. Insertion or removal of nucleotides
C. Substitution of bases
D. Termination of protein synthesis
B. Insertion or removal of nucleotides
Rationale: A frameshift mutation occurs when nucleotides are either inserted into or removed from the DNA sequence, disrupting the reading frame.
- What type of mutation results from the addition of one or several nucleotide pairs?
A. Frameshift Insertion
B. Frameshift Deletion
C. Silent Mutation
D. Transition
A. Frameshift Insertion
Rationale: A frameshift insertion mutation results from the addition of one or several nucleotide pairs, which disrupts the reading frame of codons.
- In which type of substitution is a purine base replaced with another purine or a pyrimidine replaced with another pyrimidine?
A. Transversion
B. Transition
C. Missense
D. Nonsense
B. Transition
Rationale: Transition mutations involve the substitution of a purine for a purine or a pyrimidine for a pyrimidine.
- Which mutation occurs due to the removal of one or several nucleotide pairs?
A. Silent Mutation
B. Frameshift Deletion
C. Frameshift Insertion
D. Transition
B. Frameshift Deletion
Rationale: A frameshift deletion mutation is the result of the removal of one or several nucleotide pairs, which alters the reading frame of codons.
- Which mutation changes a codon for an amino acid to a stop codon?
A. Missense Mutation
B. Silent Mutation
C. Nonsense Mutation
D. Transition
C. Nonsense Mutation
Rationale: A nonsense mutation changes a codon that codes for an amino acid into a stop codon, leading to premature termination of protein synthesis.
- Which mutation type results from a nucleotide change but doesn’t lead to a different amino acid in the protein sequence due to the genetic code’s redundancy?
A. Missense Mutation
B. Nonsense Mutation
C. Silent Mutation
D. Transition
C. Silent Mutation
Rationale: Silent mutations result from a nucleotide change but do not lead to a change in the amino acid sequence due to the redundancy of the genetic code.
- Which mutation often leads to nonfunctional proteins due to changes in the reading frame?
A. Transition
B. Transversion
C. Frameshift Mutation
D. Missense Mutation
C. Frameshift Mutation
Rationale: Frameshift mutations disrupt the three-nucleotide codon reading frame by inserting or removing nucleotides, often leading to nonfunctional proteins.
- What type of substitution involves the replacement of a purine base with a pyrimidine or vice versa?
A. Transition
B. Transversion
C. Missense
D. Nonsense
B. Transversion
Rationale: Transversion mutations involve the substitution of a purine base for a pyrimidine or a pyrimidine for a purine.
- Which mutation can be either harmful, neutral, or beneficial depending on the nature of the amino acid substitution?
A. Nonsense Mutation
B. Silent Mutation
C. Transition
D. Missense Mutation
D. Missense Mutation
Rationale: Missense mutations can vary in their impact depending on the nature of the amino acid substitution, making them potentially harmful, neutral, or even beneficial.
- What type of mutation results in a completely new sequence of codons due to the addition of nucleotides?
A. Silent Mutation
B. Missense Mutation
C. Frameshift Insertion
D. Frameshift Deletion
C. Frameshift Insertion
Rationale: Frameshift insertion results from the addition of nucleotides, creating a completely new sequence of codons.
- Which mutation is typically detrimental due to the premature termination of the protein synthesis?
A. Missense Mutation
B. Silent Mutation
C. Transition
D. Nonsense Mutation
D. Nonsense Mutation
Rationale: Nonsense mutations are typically detrimental because they introduce a stop codon prematurely, leading to the early termination of protein synthesis.
- What term describes bacteria lacking an F plasmid and pilus, and acts as the recipient during conjugation?
A. F- cells
B. Ft cells
C. Hfr cells
D. R cells
A. F- cells
Rationale: F- cells are bacteria that lack an F plasmid and pilus. They act as recipients during the process of conjugation.
- Which part of the R plasmid usually contains genes that encode resistance to several antibiotics?
A. Resistance Transfer Factor
B. Tra gene
C. F Factor
D. R Determinant
D. R Determinant
Rationale: The R Determinant of the R plasmid holds genes encoding resistance to several antibiotics.
- When is natural transformation typically triggered in bacteria?
A. During cellular division
B. At the beginning of bacterial growth
C. When nutrients run out
D. Under the influence of antibiotics
C. When nutrients run out
Rationale: Natural transformation is often triggered in bacteria when nutrients are depleted, leading to the secretion of competence pheromones.
- Which bacterial mechanism can be artificially induced by altering temperature and salt concentration?
A. Conjugation
B. Transduction
C. Induced transformation
D. Natural transformation
C. Induced transformation
Rationale: Induced transformation in bacteria, such as E. coli, can be artificially brought about by changing conditions like temperature and salt concentration.
- What does a bacteriophage do during the process of transduction?
A. It helps bacteria form a sex pilus.
B. It artificially induces competence in bacteria.
C. It mediates the transfer of DNA between bacterial cells.
D. It triggers natural transformation in bacteria.
C. It mediates the transfer of DNA between bacterial cells.
Rationale: During transduction, a bacteriophage mediates the transfer of DNA from one bacterial cell to another.
- Which of the following best describes the state of an F plasmid when it is an autonomous entity in the cytosol?
A. Integrated within the chromosome
B. Dissociated from the chromosome
C. Actively producing a sex pilus
D. Recipient during conjugation
B. Dissociated from the chromosome
Rationale: When the F plasmid is an autonomous entity in the cytosol, it is in a state where it has dissociated from the chromosome.
- Which component codes for the production of conjugation pili in bacteria?
A. R Determinant of the R plasmid
B. Tra gene in the F plasmid
C. Resistance Transfer Factor of the R plasmid
D. Competence pheromones
B. Tra gene in the F plasmid
Rationale: The tra gene, located in the F plasmid, codes for the production of the conjugation pili essential for the bacterial conjugation process.
- Which mechanism requires the presence of naked/free DNA in the environment?
A) Conjugation
B) Transduction
C) Transformation
D) Hybridization
C) Transformation
Rationale: Transformation involves the uptake of naked or free DNA from the environment by a competent recipient cell.
- For which mechanism is cell-to-cell contact a necessity?
A) Transformation
B) Conjugation
C) Transduction
D) Northern Blot
B) Conjugation
Rationale: Conjugation requires cell-to-cell contact facilitated by the F-plasmid.
- Which mechanism involves a bacteriophage for transferring genetic material?
A) Transformation
B) Conjugation
C) Transduction
D) Western Blot
C) Transduction
Rationale: Transduction involves the transfer of DNA between cells using a bacteriophage.
- In which technique can overlapping restriction fragments be detected?
A) Northern Blot
B) Southern Blot
C) Western Blot
D) Transduction
B) Southern Blot
Rationale: The Southern Blot technique is used to detect overlapping restriction fragments of DNA.
- Which blotting technique provides quantitative data about RNA synthesis?
A) Northern Blot
B) Southern Blot
C) Western Blot
D) Eastern Blot
A) Northern Blot
Rationale: The Northern Blot technique can provide quantitative information regarding RNA synthesis.
- What is primarily detected using the Western Blot technique?
A) RNA sequences
B) DNA fragments
C) Protein products of cloned genes
D) Overlapping restriction fragments
C) Protein products of cloned genes
Rationale: Western Blot uses antibodies to specifically detect protein products of cloned genes.
- Which of the following describes a competent recipient in the context of gene transfer mechanisms?
A) A cell capable of transferring DNA to another cell
B) A cell with the F-plasmid
C) A cell capable of taking up free DNA from the environment
D) A cell infected by a bacteriophage
C) A cell capable of taking up free DNA from the environment
Rationale: In the context of transformation, a competent recipient is a cell that can uptake free or naked DNA from the environment.
- What does the F-plasmid contain that facilitates conjugation?
A) Naked/free DNA
B) Gene coding for conjugation pili
C) Bacteriophage DNA
D) Antibodies
B) Gene coding for conjugation pili
Rationale: The F-plasmid contains the gene that codes for the conjugation pili, which facilitates cell-to-cell contact for gene transfer.
- In which mechanism is the recipient cell not alive?
A) Transformation
B) Conjugation
C) Transduction
D) All of the above
A) Transformation
Rationale: In transformation, the DNA in the environment can come from a dead organism, implying that the donor is not alive.
- Which technique employs antibodies for detection?
A) Northern Blot
B) Southern Blot
C) Western Blot
D) Transduction
C) Western Blot
Rationale: Western Blot uses antibodies to detect the protein products of cloned genes.
