Molecular Biology MCQs
Molecular Biology MCQs, These questions cover a wide range of topics in molecular biology and include key concepts such as DNA replication, transcription, translation, and gene regulation.
- Which of the following is the building block of DNA?
- A. Amino acids
- B. Nucleotides
- C. Monosaccharides
- D. Fatty acids
- Which enzyme is responsible for unwinding the DNA double helix during replication?
- A. DNA polymerase
- B. Helicase
- C. Ligase
- D. Primase
- What type of bond holds the two strands of DNA together?
- A. Ionic bonds
- B. Covalent bonds
- C. Hydrogen bonds
- D. Disulfide bonds
- Which of the following pairs correctly represents complementary base pairing in DNA?
- A. A-G
- B. A-T
- C. C-A
- D. C-T
- In RNA, which base is substituted for thymine found in DNA?
- A. Adenine
- B. Guanine
- C. Cytosine
- D. Uracil
- The process of copying a gene’s DNA sequence into an RNA sequence is called:
- A. Translation
- B. Transcription
- C. Replication
- D. Transformation
- Where does translation occur within the cell?
- A. Nucleus
- B. Mitochondria
- C. Ribosome
- D. Golgi apparatus
- Which of the following RNA molecules carries the genetic code from DNA to the ribosome?
- A. tRNA
- B. rRNA
- C. mRNA
- D. siRNA
- What is the main purpose of tRNA during translation?
- A. To carry amino acids to the ribosome
- B. To synthesize mRNA
- C. To form ribosomes
- D. To regulate gene expression
- The sequence of three nucleotides that codes for a specific amino acid is called a:
- A. Codon
- B. Anticodon
- C. Exon
- D. Intron
- Which enzyme synthesizes RNA from a DNA template?
- A. DNA polymerase
- B. RNA polymerase
- C. Reverse transcriptase
- D. DNA ligase
- Which type of mutation involves the substitution of a single nucleotide?
- A. Frameshift mutation
- B. Missense mutation
- C. Nonsense mutation
- D. Point mutation
- What is the function of ribosomal RNA (rRNA)?
- A. To carry genetic information
- B. To transport amino acids
- C. To form the core of the ribosome’s structure
- D. To regulate gene expression
- Which of the following processes results in the formation of a mature mRNA transcript?
- A. Replication
- B. Splicing
- C. Translation
- D. Transcription
- In which direction does DNA replication occur?
- A. 3′ to 5′
- B. 5′ to 3′
- C. Randomly
- D. Both directions simultaneously
- Which enzyme is responsible for adding RNA primers during DNA replication?
- A. DNA polymerase
- B. RNA polymerase
- C. Primase
- D. Ligase
- The lagging strand during DNA replication is synthesized in fragments called:
- A. Okazaki fragments
- B. Primosomes
- C. Nucleosomes
- D. Chromatids
- Which of the following is NOT a stop codon?
- A. UAA
- B. UAG
- C. UGA
- D. AUG
- What is the central dogma of molecular biology?
- A. RNA → DNA → Protein
- B. DNA → RNA → Protein
- C. Protein → RNA → DNA
- D. DNA → Protein → RNA
- Which molecule is the energy currency of the cell?
- A. DNA
- B. RNA
- C. ATP
- D. NADH
- What type of mutation results in a premature stop codon?
- A. Missense mutation
- B. Nonsense mutation
- C. Silent mutation
- D. Frameshift mutation
- Which of the following is a characteristic feature of eukaryotic cells but not prokaryotic cells?
- A. DNA
- B. Ribosomes
- C. Nucleus
- D. Cell membrane
- What is the function of the promoter region in DNA?
- A. To code for proteins
- B. To terminate transcription
- C. To initiate transcription
- D. To splice introns
- Which process involves the removal of introns and the joining of exons?
- A. Replication
- B. Splicing
- C. Translation
- D. Transcription
- What is the role of DNA ligase in DNA replication?
- A. To unwind the DNA helix
- B. To synthesize new DNA strands
- C. To join Okazaki fragments
- D. To add RNA primers
- Which of the following techniques can be used to amplify a specific DNA segment?
- A. Gel electrophoresis
- B. PCR (Polymerase Chain Reaction)
- C. Western blotting
- D. Northern blotting
- Which of the following is not a component of a nucleotide?
- A. Nitrogenous base
- B. Phosphate group
- C. Ribose sugar
- D. Amino acid
- What does semi-conservative replication of DNA mean?
- A. Each new DNA molecule consists of two new strands
- B. Each new DNA molecule consists of one old and one new strand
- C. Each new DNA molecule consists of two old strands
- D. Each new DNA molecule is completely new
- Which of the following pairs of processes are involved in gene expression?
- A. Replication and transcription
- B. Transcription and translation
- C. Translation and replication
- D. Transcription and splicing
- In which cellular organelle does oxidative phosphorylation occur?
- A. Nucleus
- B. Mitochondria
- C. Ribosome
- D. Endoplasmic reticulum
- Which type of RNA contains an anticodon?
- A. mRNA
- B. tRNA
- C. rRNA
- D. siRNA
- The genetic code is said to be degenerate because:
- A. Each codon specifies more than one amino acid
- B. Multiple codons can code for the same amino acid
- C. It varies between different organisms
- D. It cannot specify an amino acid
- Which of the following statements about plasmids is true?
- A. They are linear pieces of DNA
- B. They are found only in eukaryotes
- C. They can replicate independently of the chromosomal DNA
- D. They are composed of RNA
- Which of the following processes increases genetic diversity during meiosis?
- A. DNA replication
- B. Crossing over
- C. Transcription
- D. Translation
- What is a primary transcript?
- A. The initial RNA transcript synthesized from the DNA template
- B. The processed mRNA ready for translation
- C. The DNA sequence of a gene
- D. The protein product of a gene
- What is the function of a telomere?
- A. To initiate DNA replication
- B. To protect the ends of chromosomes
- C. To code for proteins
- D. To facilitate splicing
- Which of the following enzymes is involved in transcription?
- A. DNA polymerase
- B. RNA polymerase
- C. Reverse transcriptase
- D. DNA ligase
- The ribosome is made up of which two types of biological molecules?
- A. DNA and proteins
- B. RNA and lipids
- C. RNA and proteins
- D. DNA and lipids
- Which of the following statements about introns and exons is true?
- A. Introns are coding regions of a gene
- B. Exons are non-coding regions of a gene
- C. Introns are removed during RNA processing
- D. Exons are removed during RNA processing
- What is the role of enhancer sequences in gene expression?
- A. They inhibit transcription
- B. They increase the rate of transcription
- C. They are part of the mRNA
- D. They terminate transcription
- Which molecule serves as the template for protein synthesis?
- A. DNA
- B. mRNA
- C. tRNA
- D. rRNA
- The enzyme reverse transcriptase is used to synthesize:
- A. DNA from an RNA template
- B. RNA from a DNA template
- C. Proteins from an RNA template
- D. RNA from an RNA template
- During which phase of the cell cycle does DNA replication occur?
- A. G1 phase
- B. S phase
- C. G2 phase
- D. M phase
- Which of the following best describes a gene?
- A. A segment of RNA that codes for a protein
- B. A segment of DNA that codes for a protein or RNA
- C. A sequence of amino acids
- D. A type of lipid involved in cell signaling
- What role do chaperone proteins play in the cell?
- A. They assist in DNA replication
- B. They help proteins fold correctly
- C. They transport molecules across membranes
- D. They degrade misfolded proteins
- In eukaryotic cells, where does mRNA splicing occur?
- A. Cytoplasm
- B. Mitochondria
- C. Nucleus
- D. Ribosome
- What is the main function of histones in the cell?
- A. To serve as enzymes in metabolic reactions
- B. To assist in DNA packaging
- C. To facilitate RNA splicing
- D. To act as transcription factors
- Which type of RNA is involved in the regulation of gene expression?
- A. mRNA
- B. tRNA
- C. rRNA
- D. miRNA
- What is the role of the spliceosome?
- A. To transcribe DNA into RNA
- B. To translate RNA into protein
- C. To splice out introns from pre-mRNA
- D. To replicate DNA
- Which of the following best describes an operon?
- A. A group of genes regulated together
- B. A type of RNA involved in protein synthesis
- C. A segment of DNA that signals the start of transcription
- D. A protein that binds to DNA to initiate transcription
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