- Which of the following is involved in post-transcriptional regulation of gene expression?
a) DNA polymerase
b) RNA polymerase
c) MicroRNA (miRNA)
d) Topoisomerase
Answer: c) MicroRNA (miRNA)
Explanation: MicroRNAs (miRNAs) are involved in post-transcriptional regulation by binding to complementary sequences on mRNA molecules, often leading to mRNA degradation or inhibition of translation.
- The Hershey and Chase experiment, which demonstrated that DNA is the genetic material, used which of the following to label DNA?
a) Radioactive sulfur (35S)
b) Radioactive phosphorus (32P)
c) Radioactive carbon (14C)
d) Radioactive nitrogen (15N)
Answer: b) Radioactive phosphorus (32P)
Explanation: Hershey and Chase used radioactive phosphorus (32P) to label DNA because phosphorus is found in the DNA backbone but not in proteins. They used radioactive sulfur (35S) to label the protein coat of the bacteriophages.
- Which of the following best describes the function of topoisomerase during DNA replication?
a) Unwinding the DNA double helix
b) Preventing the DNA strands from tangling by relieving supercoiling
c) Synthesizing RNA primers
d) Adding nucleotides to the growing DNA strand
Answer: b) Preventing the DNA strands from tangling by relieving supercoiling
Explanation: Topoisomerase enzymes relieve the supercoiling tension generated ahead of the replication fork by temporarily cutting the DNA strands and then rejoining them.
- Which of the following types of RNA carries amino acids to the ribosome during protein synthesis?
a) mRNA
b) rRNA
c) tRNA
d) snRNA
Answer: c) tRNA
Explanation: Transfer RNA (tRNA) carries specific amino acids to the ribosome during translation, where they are added to the growing polypeptide chain.
- The phenomenon of “semi-conservative replication” in DNA means that:
a) Each new DNA molecule consists of two newly synthesized strands
b) Each new DNA molecule consists of one parental and one newly synthesized strand
c) One DNA molecule is completely new and the other is old
d) Half of the original DNA is degraded during replication
Answer: b) Each new DNA molecule consists of one parental and one newly synthesized strand
Explanation: In semi-conservative replication, each of the two new DNA molecules retains one original (parental) strand, and one newly synthesized strand, ensuring accurate duplication.
- Which enzyme initiates DNA replication by synthesizing a short RNA primer?
a) DNA polymerase
b) Primase
c) Ligase
d) Helicase
Answer: b) Primase
Explanation: Primase synthesizes a short RNA primer to provide a starting point for DNA polymerase to begin adding nucleotides during DNA replication.
- Which of the following enzymes is responsible for sealing the nicks between Okazaki fragments during DNA replication?
a) DNA polymerase
b) DNA ligase
c) Helicase
d) Primase
Answer: b) DNA ligase
Explanation: DNA ligase is responsible for joining the Okazaki fragments on the lagging strand by forming phosphodiester bonds between the sugar-phosphate backbones of adjacent DNA fragments.
- Which of the following is the correct sequence of events in translation?
a) Initiation → Elongation → Termination
b) Elongation → Initiation → Termination
c) Termination → Initiation → Elongation
d) Elongation → Termination → Initiation
Answer: a) Initiation → Elongation → Termination
Explanation: In translation, the process begins with initiation (assembly of the ribosome at the start codon), followed by elongation (addition of amino acids to the growing polypeptide chain), and ends with termination (release of the newly synthesized protein upon reaching a stop codon).
- Which of the following correctly pairs a type of RNA with its function?
a) mRNA – brings amino acids to the ribosome
b) tRNA – carries genetic information from the nucleus
c) rRNA – forms the core structure of the ribosome
d) snRNA – catalyzes peptide bond formation
Answer: c) rRNA – forms the core structure of the ribosome
Explanation: Ribosomal RNA (rRNA) forms the structural and functional core of the ribosome. tRNA brings amino acids to the ribosome, and mRNA carries the genetic information for protein synthesis. Small nuclear RNA (snRNA) is involved in splicing.
- Which of the following statements about the central dogma of molecular biology is correct?
a) DNA → Protein → RNA
b) RNA → DNA → Protein
c) DNA → RNA → Protein
d) Protein → RNA → DNA
Answer: c) DNA → RNA → Protein
Explanation: The central dogma of molecular biology states that genetic information flows from DNA to RNA through transcription and from RNA to protein through translation.
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