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A novel virus is discovered with a single-stranded nucleic acid genome. Treatment with RNase H significantly reduces its infectivity, while DNase I has no effect. Further analysis reveals the presence of short RNA fragments complementary to the genome. What can be most confidently inferred about the viral genome?
It is a single-stranded RNA virus that replicates through a DNA intermediate.
It is a single-stranded DNA virus that replicates through an RNA intermediate.
It is a single-stranded RNA virus that replicates through a double-stranded RNA intermediate.
It is a double-stranded RNA virus.
Which structural modification to a eukaryotic mRNA is MOST crucial for preventing its degradation by exonucleases in the cytoplasm?
Splicing out of introns
Methylation of specific adenine residues
Association with ribosomes
Addition of a 5' cap and a 3' poly(A) tail
A researcher isolates a nucleic acid sample and finds it contains 22% adenine. Which of the following is the MOST LIKELY composition of the sample?
22% thymine, 28% guanine, 28% cytosine
28% thymine, 22% guanine, 22% cytosine
22% uracil, 28% guanine, 28% cytosine
Equal amounts of all four bases
During DNA replication, the lagging strand is synthesized discontinuously. Which enzyme is PRIMARILY responsible for joining these discontinuous fragments?
DNA Polymerase I
DNA Polymerase III
DNA Helicase
DNA Ligase
Certain antibiotics inhibit bacterial protein synthesis by targeting the 30S ribosomal subunit. Which of the following processes related to translation would be MOST directly affected by such antibiotics?
Translocation of the ribosome along the mRNA
Formation of peptide bonds
Binding of mRNA to the ribosome
Release of the completed polypeptide chain
A mutation in a tRNA molecule alters its anticodon sequence from 3'-AUC-5' to 3'-AUA-5'. Assuming the wobble hypothesis applies, which of the following changes in protein synthesis is MOST likely to occur?
Protein synthesis will be terminated prematurely.
A different amino acid will be incorporated at the corresponding codon.
The mutant tRNA might recognize a different codon but still incorporate the same amino acid.
The mutation will have no effect on protein synthesis.
A novel enzyme is discovered that catalyzes the hydrolysis of a specific peptide bond. Kinetic studies reveal a of 10 μM and a of 50 μmol/min. A competitive inhibitor with a of 2 μM is added at a concentration of 5 μM. What will be the apparent and in the presence of the inhibitor?
Km' = 35 μM, Vmax' = 50 μmol/min
Km' = 10 μM, Vmax' = 25 μmol/min
Km' = 25 μM, Vmax' = 50 μmol/min
Km' = 35 μM, Vmax' = 25 μmol/min
Which statement BEST describes the effect of a non-competitive inhibitor on an enzyme?
It decreases the without changing the .
It increases the without changing the .
It decreases both the and the .
It increases both the and the .
An enzyme exhibiting positive cooperativity shows a sigmoidal kinetic curve. Which statement is FALSE regarding this type of enzyme?
The binding of the first substrate molecule decreases the enzyme's affinity for subsequent substrate molecules.
The enzyme likely has multiple subunits.
The Hill coefficient is greater than 1.
The enzyme's activity is more sensitive to substrate concentration changes compared to enzymes with Michaelis-Menten kinetics.
