MCQ 1. Which of the following statements is true regarding DNA?
A) DNA contains uracil instead of thymine
B) DNA is a polymer of amino acids
C) DNA stores genetic information in the sequence of nitrogenous bases
D) DNA is single-stranded in all organisms
Explanation:
• DNA is a polynucleotide composed of A, T, G, and C bases.
• Hereditary information is encoded in the specific sequence of these bases.
• Uracil is found in RNA, not in DNA.
• DNA is a polynucleotide composed of A, T, G, and C bases.
• Hereditary information is encoded in the specific sequence of these bases.
• Uracil is found in RNA, not in DNA.
MCQ 2. In which cellular organelle is DNA primarily found in eukaryotic cells?
A) Ribosome
B) Nucleus
C) Cytoplasm
D) Endoplasmic reticulum
Explanation:
• Eukaryotic DNA is mostly in the nucleus (linear chromosomes).
• Mitochondria and chloroplasts also contain circular DNA.
• Prokaryotic DNA is circular and found in nucleoid.
• Eukaryotic DNA is mostly in the nucleus (linear chromosomes).
• Mitochondria and chloroplasts also contain circular DNA.
• Prokaryotic DNA is circular and found in nucleoid.
MCQ 3. Which of the following enzymes is essential for DNA replication?
A) RNA polymerase
B) DNA polymerase
C) Ligase only
D) Reverse transcriptase
Explanation:
• DNA polymerase synthesizes new DNA strands using template strands.
• Ligase joins Okazaki fragments; reverse transcriptase is for RNA → DNA conversion.
• DNA polymerase synthesizes new DNA strands using template strands.
• Ligase joins Okazaki fragments; reverse transcriptase is for RNA → DNA conversion.
MCQ 4. Which of the following statements about DNA in eukaryotes is correct?
A) DNA is circular and located in cytoplasm
B) DNA is linear and enclosed within the nucleus
C) DNA is absent in mitochondria
D) DNA is single-stranded
Explanation:
• Eukaryotic DNA: Linear chromosomes in the nucleus, plus small circular DNA in mitochondria and chloroplasts.
• Prokaryotic DNA: Circular, located in nucleoid.
• UPSC often asks comparative questions prokaryotic vs eukaryotic DNA.
• Eukaryotic DNA: Linear chromosomes in the nucleus, plus small circular DNA in mitochondria and chloroplasts.
• Prokaryotic DNA: Circular, located in nucleoid.
• UPSC often asks comparative questions prokaryotic vs eukaryotic DNA.
MCQ 5. Which of the following techniques is directly related to DNA analysis?
A) ELISA
B) PCR (Polymerase Chain Reaction)
C) Mass spectrometry
D) X-ray crystallography
Explanation:
• PCR: Amplifies specific DNA fragments for diagnostics, forensic analysis, and research.
• ELISA: Detects proteins or antibodies.
• Mass spectrometry: Identifies molecular mass.
• X-ray crystallography: Determines 3D structure of molecules.
• PCR: Amplifies specific DNA fragments for diagnostics, forensic analysis, and research.
• ELISA: Detects proteins or antibodies.
• Mass spectrometry: Identifies molecular mass.
• X-ray crystallography: Determines 3D structure of molecules.
MCQ 6. Which of the following statements about RNA is correct?
A) RNA is always double-stranded
B) RNA contains thymine instead of uracil
C) RNA acts as a template for protein synthesis
D) RNA cannot leave the nucleus
Explanation:
• mRNA carries genetic code from DNA to ribosomes.
• RNA contains uracil instead of thymine.
• tRNA and rRNA play roles in translation.
• mRNA carries genetic code from DNA to ribosomes.
• RNA contains uracil instead of thymine.
• tRNA and rRNA play roles in translation.
MCQ 7. Which of the following genome editing technologies is based on RNA-guided endonucleases?
A) Zinc finger nucleases (ZFNs)
B) TALENs
C) CRISPR-Cas9
D) RNAi
Explanation:
• CRISPR-Cas9: Uses guide RNA to direct Cas9 enzyme to target DNA sequences for editing.
• Zinc finger and TALENs are protein-based DNA editors.
• RNAi silences gene expression at the mRNA level.
• CRISPR-Cas9: Uses guide RNA to direct Cas9 enzyme to target DNA sequences for editing.
• Zinc finger and TALENs are protein-based DNA editors.
• RNAi silences gene expression at the mRNA level.
MCQ 8. “Base editing” in genome editing refers to:
A) Replacing a DNA strand entirely
B) Changing one DNA base into another without double-strand break
C) Cutting mRNA to prevent translation
D) Cloning whole organisms
Explanation:
• Base editing allows precise single nucleotide modifications, reducing errors compared to CRISPR-Cas9 double-strand breaks.
• Base editing allows precise single nucleotide modifications, reducing errors compared to CRISPR-Cas9 double-strand breaks.
MCQ 9. Polymerase Chain Reaction (PCR) is used to:
A) Synthesize proteins
B) Amplify specific DNA fragments
C) Measure enzyme activity
D) Identify RNA structure
Explanation:
• PCR amplifies DNA exponentially for diagnostics, research, and forensics.
• Important in biotechnology and molecular medicine.
• PCR amplifies DNA exponentially for diagnostics, research, and forensics.
• Important in biotechnology and molecular medicine.
MCQ 10. Which of the following statements is true about CRISPR-Cas9 applications?
A) It can be used to treat genetic disorders
B) It can only edit bacterial genomes
C) It cannot target human genes
D) It replaces DNA with RNA sequences directly
Explanation:
• CRISPR-Cas9 is used in gene therapy, crop improvement, and pathogen resistance.
• It can target genes in plants, animals, and humans.
• CRISPR-Cas9 is used in gene therapy, crop improvement, and pathogen resistance.
• It can target genes in plants, animals, and humans.