A virus immediately produces proteins from its RNA genome after infection. The genome is:
Positive-sense RNA
Negative-sense RNA
Double-stranded RNA
The Correct Answer is A
A. Positive-sense RNA: Positive-sense RNA viruses possess genomes that function directly as messenger RNA (mRNA). After entering the host cell, the viral RNA can immediately bind to host ribosomes and begin translation to produce viral proteins. No transcription step is required before protein synthesis, these viruses can rapidly initiate replication once infection occurs.
B. Negative-sense RNA: Negative-sense RNA viruses have genomes that are complementary to mRNA and therefore cannot be translated directly by host ribosomes. Before protein synthesis can occur, the virus must first use an RNA-dependent RNA polymerase to synthesize a complementary positive-sense RNA strand. Only this newly formed RNA can function as mRNA for protein production.
C. Double-stranded RNA: Double-stranded RNA viruses contain both a positive and a negative RNA strand. However, the host cell cannot directly translate the double-stranded genome. The virus must first use viral RNA polymerase enzymes to transcribe the negative strand into a positive-sense RNA that can serve as mRNA for translation.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. a purine always bonding to a pyrimidine: This describes the complementary base-pairing rule in DNA, where adenine pairs with thymine and guanine pairs with cytosine. While important for replication fidelity, it does not define the concept of semiconservative replication.
B. one helix strand that runs from the 5' to 3' direction and the other strand runs from the 3' to 5' direction: This describes the antiparallel orientation of DNA strands, which is essential for replication and enzymatic activity but does not capture the semiconservative nature of DNA replication.
C. each base bonding at the 1' position of the sugar: This refers to the covalent attachment of nitrogenous bases to the sugar molecule in nucleotides, forming nucleosides. It is a structural detail of nucleotides but unrelated to the semiconservative replication process.
D. an original parent DNA strand and one newly synthesized DNA strand comprising a new DNA molecule: Semiconservative replication means that each daughter DNA molecule retains one original (parental) strand and contains one newly synthesized complementary strand. This mechanism ensures genetic continuity and reduces errors during cell division.
Correct Answer is D
Explanation
A. semisynthetic drugs: Semisynthetic drugs are chemically modified natural antibiotics designed to improve their stability, spectrum, or pharmacokinetic properties. While some may target gram-positive bacteria, the term does not specifically indicate activity against a narrow group of organisms.
B. antibiotics: Antibiotics are naturally occurring or derived substances that inhibit or kill microorganisms. This term refers broadly to the type of drug rather than the range of bacteria it affects, so it does not specifically describe drugs limited to gram-positive bacteria.
C. broad-spectrum drugs: Broad-spectrum drugs are effective against a wide range of bacteria, including both gram-positive and gram-negative organisms. They are used when the specific pathogen is unknown but are not limited to gram-positive bacteria.
D. narrow-spectrum drugs: Narrow-spectrum drugs are effective against a limited group of microorganisms. In this context, a drug that targets only gram-positive bacteria is considered narrow-spectrum, as it does not act against gram-negative organisms and allows for more targeted therapy with reduced impact on normal flora.
E. synthetic drugs: Synthetic drugs are entirely chemically synthesized rather than derived from natural sources. While some synthetic drugs may target gram-positive bacteria, the term describes the origin of the drug, not its spectrum of activity.
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