- The process by which DNA is transferred from one bacterium to another via a bacteriophage is called:
a) Transformation
b) Conjugation
c) Transduction
d) Transcription
Answer: c) Transduction
Explanation: Transduction is the process by which a bacteriophage (a virus that infects bacteria) transfers DNA from one bacterium to another, facilitating genetic exchange between bacteria.
- Which of the following is a key function of RNA polymerase during transcription?
a) Proofreading the newly synthesized DNA
b) Synthesizing RNA from a DNA template
c) Binding amino acids to tRNA
d) Adding a 5′ cap and poly-A tail to mRNA
Answer: b) Synthesizing RNA from a DNA template
Explanation: RNA polymerase synthesizes RNA by reading the DNA template strand and assembling complementary RNA nucleotides during transcription.
- In the Hershey-Chase experiment, which part of the bacteriophage was labeled with radioactive phosphorus?
a) Protein coat
b) DNA
c) RNA
d) Lipid envelope
Answer: b) DNA
Explanation: In the Hershey-Chase experiment, DNA was labeled with radioactive phosphorus (32P), and the protein coat was labeled with radioactive sulfur (35S). The experiment demonstrated that DNA is the genetic material.
- What is the significance of the 5′ cap and poly-A tail added to eukaryotic mRNA?
a) They help in mRNA splicing
b) They signal termination of transcription
c) They protect mRNA from degradation and help in translation initiation
d) They mark the mRNA for degradation by nucleases
Answer: c) They protect mRNA from degradation and help in translation initiation
Explanation: The 5′ cap and poly-A tail are important for protecting the mRNA from degradation by nucleases and play a role in the initiation of translation by ribosomes.
- Which of the following is true about gene expression in prokaryotes?
a) Transcription occurs in the nucleus, and translation occurs in the cytoplasm
b) mRNA processing involves the addition of a 5′ cap and poly-A tail
c) Transcription and translation occur simultaneously
d) Introns are removed from mRNA before translation
Answer: c) Transcription and translation occur simultaneously
Explanation: In prokaryotes, transcription and translation are coupled, meaning that translation begins before transcription is complete since both processes occur in the cytoplasm and there is no nuclear membrane separating them.
- In eukaryotes, which of the following elements enhances the transcription of a gene located far from its site?
a) Promoter
b) Operator
c) Silencer
d) Enhancer
Answer: d) Enhancer
Explanation: Enhancers are DNA sequences that can increase the transcription of a gene even if they are located far from the gene they regulate. They function by interacting with specific transcription factors to enhance gene expression.
- Which of the following best describes a silent mutation?
a) A mutation that changes an amino acid codon into a stop codon
b) A mutation that does not change the amino acid sequence of the protein
c) A mutation that shifts the reading frame
d) A mutation that deletes large segments of DNA
Answer: b) A mutation that does not change the amino acid sequence of the protein
Explanation: A silent mutation is a point mutation in the DNA sequence that does not result in a change in the amino acid sequence of the protein, often due to the redundancy of the genetic code.
- Which of the following enzymes is responsible for the synthesis of the lagging strand during DNA replication?
a) DNA polymerase I
b) DNA polymerase III
c) Ligase
d) Primase
Answer: b) DNA polymerase III
Explanation: DNA polymerase III synthesizes the lagging strand in short fragments called Okazaki fragments. DNA polymerase I removes RNA primers and fills in the gaps with DNA, while DNA ligase joins the fragments.
- Which of the following enzymes is responsible for relieving the supercoiling tension ahead of the replication fork?
a) Helicase
b) DNA polymerase
c) Topoisomerase
d) Ligase
Answer: c) Topoisomerase
Explanation: Topoisomerase helps to relieve the supercoiling tension ahead of the replication fork that is caused by the unwinding of the DNA double helix. It cuts and rejoins the DNA to prevent tangling.
- Which of the following is the role of tRNA during translation?
a) Synthesizes mRNA from a DNA template
b) Carries amino acids to the ribosome
c) Catalyzes the formation of peptide bonds
d) Regulates transcription
Answer: b) Carries amino acids to the ribosome
Explanation: Transfer RNA (tRNA) carries specific amino acids to the ribosome, where the anticodon on tRNA pairs with the corresponding codon on mRNA during protein synthesis, allowing the ribosome to link amino acids into a growing polypeptide chain.
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