If the wild type DNA sequence reads THE CAT ATE THE BIG RAT, what type of mutation would change the sequence to THE CAT ATE (stop)?
Deletion
Nonsense
Silent
Missense
Insertion
The Correct Answer is B
A. Deletion: A deletion mutation removes one or more nucleotides from the DNA sequence. While deletions can lead to frameshifts and potentially premature stop codons, the key feature in this scenario is the introduction of a stop signal, not the removal of nucleotides per se.
B. Nonsense: A nonsense mutation changes a codon that encodes an amino acid into a stop codon. In this example, “THE CAT ATE THE BIG RAT” is truncated to “THE CAT ATE (stop),” indicating translation terminates prematurely. This type of mutation produces a truncated, usually nonfunctional protein.
C. Silent: A silent mutation changes a nucleotide without altering the amino acid sequence. It does not produce a stop codon or truncate the protein, so it would not result in “THE CAT ATE (stop).”
D. Missense: A missense mutation changes a codon so that a different amino acid is incorporated. While it alters the protein sequence, it does not introduce a stop codon, so it cannot account for the premature termination seen here.
E. Insertion: An insertion adds one or more nucleotides into the sequence. Like deletions, insertions can cause frameshifts that might eventually produce a stop codon, but the defining characteristic in this example is the direct conversion of a codon to a stop codon, making this a nonsense mutation rather than a generic insertion.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. FAD: FAD (flavin adenine dinucleotide) acts as an electron carrier during cellular respiration, accepting electrons to become FADH₂ in the Krebs cycle. However, it is not the final electron acceptor; it only temporarily shuttles electrons to the electron transport chain.
B. Oxygen: Oxygen is the final electron acceptor in aerobic respiration. At the end of the electron transport chain, oxygen accepts electrons and combines with protons to form water. This step is critical for maintaining the flow of electrons and enabling ATP synthesis via oxidative phosphorylation.
C. Cytochrome c: Cytochrome c is an intermediate electron carrier in the mitochondrial electron transport chain. It transfers electrons between complexes but does not serve as the terminal acceptor of electrons.
D. Pyruvic acid: Pyruvic acid is the end product of glycolysis and can be further metabolized in the Krebs cycle or fermentation pathways. It does not function as an electron acceptor in aerobic respiration.
E. Nitrate: Nitrate can serve as a final electron acceptor in anaerobic respiration for certain bacteria, but in aerobic respiration, oxygen is the ultimate acceptor that drives the complete oxidation of glucose.
Correct Answer is C
Explanation
A. semisynthetic drugs: Semisynthetic drugs are chemically modified natural antibiotics. They may have improved stability, spectrum, or pharmacokinetics compared to their natural counterparts, but the term does not define the range of microbial types they affect.
B. narrow-spectrum drugs: Narrow-spectrum drugs are effective against a limited group of microorganisms, such as only Gram-positive bacteria or a specific genus. They are preferred when the causative agent is known to reduce disruption of normal microbiota and minimize resistance development.
C. broad-spectrum drugs: Broad-spectrum drugs are effective against a wide variety of microorganisms, including both Gram-positive and Gram-negative bacteria, and sometimes other microbial types. They are useful for empirical therapy when the causative agent is unknown but carry a higher risk of promoting resistance and disrupting normal flora.
D. antibiotics: Antibiotics are substances produced by microorganisms that inhibit or kill other microbes. This term describes the source or mechanism rather than the range of effectiveness; some antibiotics can be narrow- or broad-spectrum.
E. synthetic drugs: Synthetic drugs are entirely chemically synthesized rather than derived from natural sources. Like semisynthetic drugs, the term indicates origin, not the spectrum of activity.
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