1. What is the shape of the DNA molecule?
- A) Helical
- B) Linear
- C) Circular
- D) Spherical
Answer: A
Explanation: DNA has a helical structure, commonly referred to
as a double helix.
2. Who discovered the structure of DNA?
- A) James Watson and Francis Crick
- B) Rosalind Franklin and Maurice Wilkins
- C) Charles Darwin
- D) Gregor Mendel
Answer: A
Explanation: James Watson and Francis Crick, with the help of
Rosalind Franklin’s X-ray diffraction images, discovered the structure of DNA in
1953.
3. Which of the following is NOT a nitrogenous base found in DNA?
- A) Adenine
- B) Guanine
- C) Uracil
- D) Cytosine
Answer: C
Explanation: Uracil is found in RNA, not DNA. DNA contains
thymine instead of uracil.
4. In a DNA molecule, adenine always pairs with:
- A) Guanine
- B) Thymine
- C) Cytosine
- D) Uracil
Answer: B
Explanation: In DNA, adenine (A) always pairs with thymine (T)
via two hydrogen bonds.
5. Which of the following enzymes is responsible for unwinding the DNA
double helix during replication?
- A) DNA polymerase
- B) Ligase
- C) Helicase
- D) Primase
Answer: C
Explanation: Helicase unwinds the DNA double helix by breaking
the hydrogen bonds between the base pairs.
6. What is the function of DNA polymerase?
- A) To unwind the DNA
- B) To synthesize RNA
- C) To synthesize a complementary strand of DNA
- D) To add primers
Answer: C
Explanation: DNA polymerase synthesizes a complementary strand
of DNA by adding nucleotides to the growing strand.
7. In the DNA replication process, the lagging strand is synthesized in:
- A) A continuous manner
- B) A discontinuous manner
- C) A reverse manner
- D) A straight-line manner
Answer: B
Explanation: The lagging strand is synthesized in a
discontinuous manner because it is oriented in the opposite direction to the
replication fork.
8. What is the role of RNA primer in DNA replication?
- A) To initiate the replication process
- B) To provide energy for replication
- C) To join Okazaki fragments
- D) To unwind the DNA
Answer: A
Explanation: The RNA primer provides a starting point for DNA
polymerase to begin DNA synthesis.
9. What is the significance of the central dogma of molecular biology?
- A) It explains the flow of genetic information
- B) It explains the structure of DNA
- C) It defines the process of protein folding
- D) It explains how genes are inherited
Answer: A
Explanation: The central dogma explains the flow of genetic
information from DNA to RNA to protein.
10. Which of the following processes converts DNA into RNA?
- A) Replication
- B) Transcription
- C) Translation
- D) Mutation
Answer: B
Explanation: Transcription is the process by which DNA is
transcribed into RNA.
11. Which of the following is the function of ribosomes during
translation?
- A) To synthesize DNA
- B) To attach tRNA to mRNA
- C) To synthesize RNA
- D) To catalyze protein synthesis
Answer: D
Explanation: Ribosomes are the site of protein synthesis and
catalyze the process of translation.
12. The process of translation occurs in the:
- A) Nucleus
- B) Mitochondria
- C) Ribosome
- D) Chloroplast
Answer: C
Explanation: Translation takes place in the ribosomes, where
mRNA is translated into a polypeptide chain.
13. In the genetic code, a codon consists of:
- A) Two nucleotides
- B) Three nucleotides
- C) Four nucleotides
- D) One nucleotide
Answer: B
Explanation: A codon is a sequence of three nucleotides in mRNA
that codes for a specific amino acid.
14. Which of the following is an example of a point mutation?
- A) Deletion
- B) Substitution
- C) Insertion
- D) All of the above
Answer: B
Explanation: A point mutation is a mutation that affects a
single nucleotide base, such as a substitution.
15. What is the function of the 5' cap added to mRNA?
- A) To protect the mRNA from degradation
- B) To help mRNA bind to the ribosome
- C) To initiate transcription
- D) To allow mRNA to exit the nucleus
Answer: A
Explanation: The 5' cap protects mRNA from degradation and
helps in ribosome binding during translation.
16. Which of the following is the process of protein synthesis from
mRNA?
- A) Replication
- B) Translation
- C) Transcription
- D) Replication and transcription
Answer: B
Explanation: Translation is the process where mRNA is used as a
template to synthesize proteins.
17. Which type of RNA carries the genetic information from DNA to the
ribosome?
- A) tRNA
- B) rRNA
- C) mRNA
- D) hnRNA
Answer: C
Explanation: mRNA (messenger RNA) carries the genetic
information from the DNA to the ribosomes for protein synthesis.
18. Which of the following is true about tRNA?
- A) It carries the amino acid to the ribosome
- B) It carries the genetic code to the ribosome
- C) It is synthesized in the nucleus
- D) It directly codes for protein synthesis
Answer: A
Explanation: tRNA (transfer RNA) carries amino acids to the
ribosome during translation.
19. What is the name of the process by which a cell divides to form
gametes?
- A) Mitosis
- B) Meiosis
- C) Binary fission
- D) Cytokinesis
Answer: B
Explanation: Meiosis is the process by which a diploid cell
divides to form haploid gametes (sperm and egg).
20. What is the role of the operator in an operon?
- A) To bind RNA polymerase
- B) To bind repressor proteins
- C) To synthesize proteins
- D) To produce mRNA
Answer: B
Explanation: The operator is a sequence of DNA that binds
repressor proteins, which can block the transcription of genes in the operon.
21. Which of the following is the function of the promoter region in an
operon?
- A) To prevent the binding of RNA polymerase
- B) To synthesize RNA
- C) To bind RNA polymerase and initiate transcription
- D) To regulate gene expression
Answer: C
Explanation: The promoter region is where RNA polymerase binds
to initiate transcription.
22. Which enzyme is responsible for joining the Okazaki fragments on the
lagging strand during DNA replication?
- A) Helicase
- B) Ligase
- C) DNA polymerase
- D) Primase
Answer: B
Explanation: Ligase joins the Okazaki fragments on the lagging
strand by forming phosphodiester bonds between them.
23. The process of gene expression involves which of the following
steps?
- A) Transcription and translation
- B) Replication and transcription
- C) Replication and translation
- D) Mutation and translation
Answer: A
Explanation: Gene expression involves transcription (DNA to
RNA) followed by translation (RNA to protein).
24. Which of the following is true about the structure of RNA?
- A) RNA is double-stranded
- B) RNA contains the base thymine
- C) RNA contains the sugar ribose
- D) RNA is not involved in protein synthesis
Answer: C
Explanation: RNA contains the sugar ribose, unlike DNA, which
contains deoxyribose.
25. Which of the following mutations results in a change in the amino
acid sequence of a protein?
- A) Silent mutation
- B) Missense mutation
- C) Nonsense mutation
- D) Frameshift mutation
Answer: B
Explanation: A missense mutation results in the substitution of
one amino acid for another in the protein sequence.
26. What is the main function of the exon regions of a gene?
- A) To code for non-coding proteins
- B) To be spliced out during RNA processing
- C) To code for the protein sequence
- D) To regulate gene expression
Answer: C
Explanation: Exons are the coding regions of a gene that are
spliced together to form mature mRNA.
27. The process of DNA replication is said to be:
- A) Conservative
- B) Semiconservative
- C) Dispersive
- D) Non-conservative
Answer: B
Explanation: DNA replication is semiconservative, meaning each
new DNA molecule contains one old strand and one new strand.
28. The genetic code is said to be:
- A) Ambiguous
- B) Universal
- C) Specific to prokaryotes
- D) Specific to eukaryotes
Answer: B
Explanation: The genetic code is universal, meaning it is the
same for almost all organisms.
29. Which of the following is the correct order of events in
translation?
- A) Elongation → Initiation → Termination
- B) Initiation → Elongation → Termination
- C) Initiation → Termination → Elongation
- D) Elongation → Termination → Initiation
Answer: B
Explanation: The correct order of events in translation is
initiation, elongation, and termination.
30. Which of the following is a function of the 3' poly-A tail added to
mRNA?
- A) To protect mRNA from degradation
- B) To initiate transcription
- C) To help in ribosome binding
- D) To prevent the formation of introns
Answer: A
Explanation: The poly-A tail protects mRNA from degradation and
aids in the export of mRNA from the nucleus.
31. Which of the following processes occurs first during the central
dogma?
- A) Translation
- B) Replication
- C) Transcription
- D) Mutation
Answer: C
Explanation: Transcription occurs first as the DNA is
transcribed into mRNA before translation occurs in the cytoplasm.
32. What is the function of the lac operon in bacteria?
- A) To replicate the DNA
- B) To digest lactose
- C) To repair DNA
- D) To synthesize RNA
Answer: B
Explanation: The lac operon regulates the breakdown of lactose
in bacteria. It controls the expression of genes that help digest lactose when
it is available.
33. What is the function of the DNA ligase enzyme?
- A) To unwind the DNA
- B) To join Okazaki fragments
- C) To add nucleotides to the growing strand
- D) To initiate transcription
Answer: B
Explanation: DNA ligase is responsible for joining the Okazaki
fragments on the lagging strand during DNA replication.
34. What is the first step in the process of translation?
- A) Binding of mRNA to the ribosome
- B) Binding of tRNA to mRNA
- C) Formation of peptide bonds
- D) Formation of the transcription complex
Answer: A
Explanation: The first step in translation is the binding of
mRNA to the ribosome.
35. Which enzyme is responsible for synthesizing the RNA strand during
transcription?
- A) RNA polymerase
- B) DNA polymerase
- C) Ligase
- D) Helicase
Answer: A
Explanation: RNA polymerase is responsible for synthesizing RNA
from a DNA template during transcription.
36. Which of the following is the most common type of mutation?
- A) Point mutation
- B) Chromosomal mutation
- C) Insertion mutation
- D) Deletion mutation
Answer: A
Explanation: Point mutations, which involve a change in a
single nucleotide, are the most common type of mutation.
37. Which of the following is a characteristic of a virus?
- A) It is made of proteins only
- B) It can replicate independently
- C) It contains DNA or RNA but not both
- D) It contains ribosomes
Answer: C
Explanation: Viruses contain either DNA or RNA, but not both,
and they cannot replicate independently without a host cell.
38. Which of the following is NOT true about RNA processing?
- A) Introns are spliced out
- B) Exons are joined together
- C) A 5' cap is added to the RNA
- D) A poly-A tail is removed
Answer: D
Explanation: The poly-A tail is added to RNA during processing,
not removed.
39. What does the process of DNA transcription result in?
- A) mRNA
- B) tRNA
- C) Protein
- D) Ribosomal RNA
Answer: A
Explanation: Transcription results in the formation of mRNA,
which carries the genetic code from the DNA to the ribosomes.
40. What is the function of the sigma factor in prokaryotic
transcription?
- A) To promote RNA synthesis
- B) To initiate the binding of RNA polymerase to DNA
- C) To remove introns
- D) To add a 5' cap
Answer: B
Explanation: The sigma factor helps RNA polymerase bind to the
promoter region to initiate transcription in prokaryotes.
41. What is the end product of the process of transcription?
- A) Protein
- B) DNA
- C) mRNA
- D) rRNA
Answer: C
Explanation: The end product of transcription is mRNA, which is
used as a template for protein synthesis in translation.
42. Which of the following enzymes is involved in proofreading DNA
during replication?
- A) DNA polymerase
- B) RNA polymerase
- C) Ligase
- D) Topoisomerase
Answer: A
Explanation: DNA polymerase has proofreading activity and
ensures that the newly synthesized DNA strand is correct.
43. Which type of RNA is involved in the regulation of gene expression
and plays a role in RNA interference?
- A) mRNA
- B) rRNA
- C) tRNA
- D) miRNA
Answer: D
Explanation: miRNA (microRNA) regulates gene expression by
binding to mRNA and preventing its translation.
44. What does the term 'genetic code' refer to?
- A) The sequence of amino acids in a protein
- B) The sequence of nucleotides in RNA
- C) The sequence of nucleotides in DNA that codes for proteins
- D) The sequence of nucleotides in DNA that does not code for proteins
Answer: C
Explanation: The genetic code refers to the sequence of
nucleotides in DNA that codes for proteins.
45. What is the difference between prokaryotic and eukaryotic
transcription?
- A) Prokaryotes do not have RNA polymerase
- B) Eukaryotes have a nucleus where transcription occurs
- C) Prokaryotes do not have introns
- D) Eukaryotes do not have a genetic code
Answer: B
Explanation: In eukaryotes, transcription occurs in the
nucleus, whereas in prokaryotes, it occurs in the cytoplasm.
46. Which of the following does NOT occur in the process of DNA
replication?
- A) Formation of the replication bubble
- B) Synthesis of RNA primers
- C) Unwinding of DNA by helicase
- D) Formation of the mRNA strand
Answer: D
Explanation: mRNA is not formed during DNA replication; it is
synthesized during transcription.
47. Which of the following is TRUE about the genetic material in
viruses?
- A) It is always DNA
- B) It can be either DNA or RNA
- C) It is never single-stranded
- D) It is always double-stranded
Answer: B
Explanation: Viruses can have either DNA or RNA as their
genetic material, and it can be single or double-stranded.
48. What is the function of a promoter in a gene?
- A) To start the process of translation
- B) To signal the end of transcription
- C) To help in the binding of RNA polymerase
- D) To add a cap to the RNA molecule
Answer: C
Explanation: The promoter is a region of DNA that signals where
RNA polymerase should bind to initiate transcription.
49. What is the key difference between eukaryotic and prokaryotic
translation?
- A) Eukaryotes have ribosomes in the cytoplasm, while prokaryotes do not
- B) Translation occurs in the cytoplasm in both, but in prokaryotes, it starts
before transcription ends
- C) Eukaryotes do not have ribosomes
- D) Translation is not required in eukaryotes
Answer: B
Explanation: In prokaryotes, translation can begin before
transcription is complete, while in eukaryotes, transcription and translation
are separate processes.
50. Which of the following is NOT true about eukaryotic gene expression?
- A) It involves the removal of introns
- B) It includes the formation of mRNA
- C) It involves the use of ribosomes in the cytoplasm
- D) It requires RNA polymerase II for transcription
Answer: C
Explanation: Ribosomes are involved in translation, not gene
expression itself. Gene expression includes processes like transcription and RNA
processing.