1. What is the role of DNA polymerase during DNA replication?
Correct Answer: C
DNA polymerase adds nucleotides to the growing DNA strand following the template strand. This is its primary function in replication.
Tip: Polymerase builds polymers—think "strand extender."
2. Which statement best defines the scientific method?
Correct Answer: B
The scientific method involves forming questions, creating hypotheses, and systematically testing them with experiments and observations.
Tip: Remember: method = systematic, not random.
3. Which subatomic particle determines the chemical properties of an element?
Electrons, especially those in the outermost shell (valence electrons), determine how an atom interacts chemically with other atoms.
Tip: Electrons = chemistry; nucleus = identity.
4. According to the central dogma of molecular biology, which pathway is correct?
The central dogma describes the flow of genetic information: DNA is transcribed into RNA, which is translated into protein.
Tip: Think “DNA makes RNA makes Protein” → “D → R → P.”
5. Which type of RNA carries amino acids to the ribosome during translation?
tRNA (transfer RNA) brings amino acids to the ribosome and matches them to the codons on the mRNA during translation.
Tip: tRNA = “taxi” for amino acids.
6. Which molecule stores genetic information in cells?
DNA (deoxyribonucleic acid) contains the hereditary instructions for cells and organisms.
Tip: DNA = “blueprint of life.”
7. Which bond holds together complementary DNA bases?
Hydrogen bonds connect complementary base pairs (A–T, G–C) across the two DNA strands.
Tip: Think “H-bonds hold the rungs of the ladder.”
8. Which type of bond is broken during DNA denaturation?
Hydrogen bonds between complementary DNA bases are disrupted during denaturation, separating the two strands.
Tip: Denaturation = strand separation by breaking “weak H-bonds.”
9. What is the function of ribosomes?
Ribosomes translate mRNA sequences into amino acid chains, forming proteins.
Tip: Ribosome = “protein factory.”
10. Which is NOT a component of an atom?
Correct Answer: D
Molecules are combinations of atoms, not components of a single atom.
Tip: Atom = building block; molecule = assembly of blocks.
11. During transcription, which enzyme synthesizes RNA from a DNA template?
RNA polymerase binds to the DNA template and synthesizes complementary RNA during transcription.
Tip: RNA polymerase = “RNA builder.”
12. Which base pairs with adenine in DNA?
In DNA, adenine (A) forms hydrogen bonds with thymine (T).
Tip: Remember “A–T and G–C” rule for DNA.
13. What is the main function of mRNA?
mRNA carries the DNA sequence (genetic code) from the nucleus to the ribosomes for translation.
Tip: mRNA = messenger carrying instructions.
14. Which of the following is NOT a nitrogenous base in DNA?
Uracil is present in RNA, not DNA.
Tip: DNA = A, T, G, C; RNA uses U instead of T.
15. Which process converts DNA into RNA?
Transcription is the process where RNA is synthesized using DNA as a template.
Tip: Transcription = “DNA → RNA.”
16. Which macromolecule is primarily responsible for catalyzing chemical reactions in cells?
Enzymes, which are proteins, speed up chemical reactions by lowering activation energy.
Tip: Enzymes = protein catalysts.
17. Which of the following is a purine base?
Correct Answer: A
Adenine is a purine, which has a double-ring structure. Guanine is also a purine; cytosine, thymine, and uracil are pyrimidines.
Tip: Purines = “big double rings” (A, G).
18. Which molecule is considered the “energy currency” of the cell?
ATP (adenosine triphosphate) stores and transfers energy for cellular processes.
Tip: ATP = ready-to-use energy for the cell.
19. During translation, which sequence of nucleotides specifies a single amino acid?
A codon is a triplet of nucleotides on mRNA that specifies one amino acid.
Tip: Codon = 3 letters = 1 amino acid.
20. Which component of DNA forms the backbone of the molecule?
The sugar-phosphate backbone consists of alternating phosphate groups and deoxyribose sugars, forming the structural framework of DNA.
Tip: Backbone = sugar + phosphate chain.
21. What is the complementary DNA sequence for 5'-ATCG-3'?
Complementary DNA strands pair A–T and G–C, with opposite orientation (antiparallel). Thus, 5'-ATCG-3' pairs with 3'-TAGC-5'.
Tip: DNA is antiparallel—always reverse direction for the complementary strand.
22. What is the primary function of ligase in DNA replication?
DNA ligase joins Okazaki fragments on the lagging strand, forming a continuous DNA strand.
Tip: Ligase = “glue” for DNA fragments.
23. Which of the following best describes a gene?
A gene is a DNA sequence that contains instructions for making RNA or protein products.
Tip: Gene = DNA segment coding for function.
24. Which RNA molecule forms part of the ribosome?
rRNA (ribosomal RNA) is a structural and catalytic component of ribosomes.
Tip: rRNA = “ribosome RNA.”
25. Which of the following correctly pairs a pyrimidine with a purine?
In DNA, pyrimidines (C, T) pair with purines (A, G). Cytosine (pyrimidine) pairs with Guanine (purine).
Tip: Remember: “C–G” and “A–T” for DNA base pairing.
26. Which enzyme unwinds the DNA double helix during replication?
Helicase unwinds the DNA double helix, creating replication forks for DNA synthesis.
Tip: Helicase = “unzipping enzyme.”
27. Which type of RNA contains the anticodon?
tRNA carries amino acids and contains the anticodon, which pairs with the codon on mRNA during translation.
Tip: tRNA = “anticodon carrier.”
28. Which of the following is NOT a stage of the scientific method?
Random guessing is not part of the systematic scientific method, which relies on observation, hypothesis, and testing.
Tip: Scientific method = systematic, not random.
29. Which element is most abundant in organic molecules?
Carbon is the backbone of all organic molecules, including carbohydrates, proteins, lipids, and nucleic acids.
Tip: Think “organic chemistry = carbon chemistry.”
30. Which base pairs are held together by three hydrogen bonds?
Guanine–Cytosine pairs are connected by three hydrogen bonds, making them more stable than A–T pairs (two hydrogen bonds).
Tip: G–C = “strong triple bond” for DNA stability.
31. During translation, where does the polypeptide chain form?
Translation occurs on ribosomes in the cytoplasm, where tRNA brings amino acids to assemble the polypeptide chain.
Tip: Ribosome = “factory site” for protein assembly.
32. Which macromolecule contains both nitrogen and phosphorus?
Nucleic acids (DNA and RNA) contain nitrogenous bases and phosphate groups, incorporating both nitrogen and phosphorus.
Tip: Nucleic acids = N + P.
33. Which component of the scientific method comes immediately after forming a hypothesis?
After forming a hypothesis, experiments are designed and conducted to test it systematically.
Tip: Hypothesis → Test (experiment) → Analyze → Conclude.
34. Which of the following is a function of rRNA?
rRNA provides the structural framework and catalytic activity for ribosomes.
Tip: rRNA = scaffold + catalyst in ribosomes.
35. Which type of molecule is composed of nucleotide monomers?
Nucleic acids (DNA and RNA) are polymers of nucleotides, which include a sugar, phosphate, and nitrogenous base.
Tip: Nucleotide = building block of nucleic acids.
36. Which of the following correctly describes the “central dogma” of molecular biology?
The central dogma states that genetic information flows from DNA to RNA (transcription) and then RNA to protein (translation).
Tip: Remember: DNA = blueprint, RNA = messenger, Protein = product.
37. What type of bond forms between amino acids in a polypeptide?
Peptide bonds covalently link amino acids to form a polypeptide chain.
Tip: Peptide bond = protein backbone connection.
38. Which of the following is a characteristic unique to RNA compared to DNA?
RNA contains uracil instead of thymine, distinguishing it from DNA.
Tip: RNA = U replaces T.
39. What is the role of primase during DNA replication?
Primase synthesizes short RNA primers that provide a starting point for DNA polymerase to add nucleotides.
Tip: Primase = “primer maker.”
40. Which type of bond stabilizes the secondary structure of proteins (alpha helices and beta sheets)?
Hydrogen bonds between backbone atoms stabilize secondary protein structures.
Tip: H-bonds = alpha helix & beta sheet stability.
41. Which process involves the synthesis of a complementary DNA strand from an existing DNA template?
DNA replication produces a complementary DNA strand using the original strand as a template.
Tip: Replication = “copying DNA.”
42. Which type of bond connects nucleotides in a single DNA strand?
Phosphodiester bonds link the sugar of one nucleotide to the phosphate of the next, forming the backbone of DNA.
Tip: Phosphodiester bond = sugar-phosphate connection.
43. What is the primary function of tRNA?
tRNA carries specific amino acids to the ribosome and matches them with codons on the mRNA.
Tip: tRNA = “amino acid taxi.”
44. Which of the following is NOT a nitrogenous base in DNA?
Uracil is found in RNA, not DNA.
Tip: DNA = A, T, G, C; RNA = U replaces T.
45. What is the complementary RNA sequence to DNA 3'-GATC-5'?
RNA pairs complementary bases with DNA, replacing T with U. 3'-GATC-5' DNA → 5'-CUAG-3' RNA.
Tip: Transcribe DNA → RNA, A–U, G–C, antiparallel.
46. Which of the following best describes an Okazaki fragment?
Okazaki fragments are short DNA segments synthesized discontinuously on the lagging strand during replication.
Tip: Lagging strand = “broken into Okazaki fragments.”
47. During transcription, which enzyme synthesizes RNA from a DNA template?
RNA polymerase reads the DNA template and synthesizes a complementary RNA strand during transcription.
48. What is the main difference between the leading and lagging strands during DNA replication?
The leading strand is synthesized continuously toward the replication fork, while the lagging strand is synthesized in Okazaki fragments away from the fork.
Tip: Leading = smooth; Lagging = fragmented.
49. Which of the following is a function of the 5' cap added to eukaryotic mRNA?
The 5' cap protects eukaryotic mRNA from degradation and assists in ribosome binding for translation.
Tip: 5' cap = “mRNA protective hat.”
50. Which of the following best explains why G–C rich regions are more thermally stable than A–T rich regions?
G–C pairs form three hydrogen bonds, making the DNA region more stable against heat than A–T pairs, which have only two hydrogen bonds.
Tip: More H-bonds = more thermal stability.
51. What is the primary function of the poly-A tail on eukaryotic mRNA?
The poly-A tail is a sequence of adenines at the 3' end of eukaryotic mRNA that stabilizes it and prevents rapid degradation.
Tip: Poly-A tail = “mRNA life jacket.”
52. During translation, which site of the ribosome holds the growing polypeptide chain?
The P site (peptidyl site) of the ribosome holds the tRNA with the growing polypeptide chain.
Tip: P = “peptide chain holder.”
53. Which molecule carries the genetic code from DNA to the ribosome?
mRNA transmits the genetic code from DNA in the nucleus to ribosomes in the cytoplasm.
Tip: mRNA = “messenger RNA.”
54. Which statement best describes a codon?
A codon is a triplet of RNA nucleotides on mRNA that specifies a particular amino acid during translation.
55. In eukaryotic cells, where does transcription occur?
Transcription occurs in the nucleus, where DNA serves as the template for RNA synthesis.
Tip: DNA stays in the nucleus; RNA goes out to cytoplasm.
56. Which process converts the information in mRNA into a polypeptide?
Translation reads the mRNA sequence and synthesizes a polypeptide chain at the ribosome.
Tip: Translation = “RNA → protein.”
57. Which component of DNA determines the sequence of amino acids in proteins?
The order of nitrogenous bases in DNA (A, T, G, C) encodes the sequence of amino acids in proteins.
Tip: Bases = “letters of genetic code.”
58. Which of the following is true about ribosomes?
Ribosomes consist of ribosomal RNA (rRNA) and proteins and are the sites of protein synthesis.
Tip: Ribosome = protein factory made of protein + rRNA.
59. What is the anticodon of tRNA that pairs with the mRNA codon 5’-AUG-3’?
tRNA anticodon is complementary and antiparallel to mRNA codon. mRNA 5’-AUG-3’ pairs with tRNA 3’-UAC-5’.
Tip: Always read codon 5’→3’ and match anticodon 3’→5’.
60. Which enzyme joins Okazaki fragments on the lagging strand?
DNA ligase seals the sugar-phosphate backbone, connecting Okazaki fragments into a continuous strand.
Tip: Ligase = “DNA glue.”
61. Which statement is true about transcription in prokaryotes?
Prokaryotes lack a nucleus, so transcription occurs in the cytoplasm.
Tip: Prokaryote = everything happens in cytoplasm.
62. Which molecule is directly decoded to form a protein?
mRNA is read by the ribosome to assemble amino acids into a polypeptide chain.
Tip: mRNA = “instructions read at ribosome.”
63. Which of the following describes a promoter?
Promoters are DNA sequences where RNA polymerase binds to initiate transcription.
Tip: Promoter = “transcription start signal.”
64. Which of the following best describes an exon?
Exons are sequences in RNA that remain after splicing and code for proteins.
Tip: Exons = “expressed sequences.”
65. Which of the following correctly pairs the nitrogenous bases in RNA?
In RNA, adenine pairs with uracil (A–U) and guanine pairs with cytosine (G–C).
Tip: RNA: U replaces T; G–C stays the same.
66. Which molecule provides the energy for adding nucleotides during DNA replication?
Deoxyribonucleotide triphosphates (dNTPs) are the building blocks of DNA; their high-energy phosphate bonds drive polymerization.
Tip: dNTPs = “DNA bricks with built-in energy.”
67. Which process removes introns from pre-mRNA in eukaryotes?
Splicing removes introns from pre-mRNA, leaving exons to be joined into mature mRNA.
Tip: Splicing = “cutting out non-coding sequences.”
68. Which amino acid does the start codon AUG code for?
The start codon AUG codes for methionine, which initiates protein synthesis.
Tip: AUG = “always start with Methionine.”
69. Which type of RNA carries amino acids to the ribosome?
tRNA brings amino acids to the ribosome and matches them to codons on the mRNA.
Tip: tRNA = “amino acid delivery truck.”
70. What is the main difference between DNA and RNA sugar molecules?
DNA contains deoxyribose (lacking 2’ OH), while RNA contains ribose.
Tip: DNA = deoxy, RNA = ribose.
71. Which of the following is true about the lagging strand?
The lagging strand is synthesized in short Okazaki fragments away from the replication fork.
Tip: Lagging = fragmented, requires ligase.
72. Which enzyme unwinds the DNA double helix during replication?
Helicase breaks hydrogen bonds between base pairs, unwinding the DNA helix.
Tip: Helicase = “DNA zipper opener.”
73. Which of the following is complementary to DNA strand 5’-ATCG-3’ in RNA?
Transcription makes RNA complementary and antiparallel: DNA 5’-ATCG-3’ → RNA 3’-UAGC-5’.
Tip: Transcribe 5’→3’ DNA to 3’→5’ RNA; replace T with U.
74. What type of macromolecule is DNA?
DNA is a nucleic acid composed of nucleotides (sugar, phosphate, base).
Tip: DNA = nucleic acid, RNA too.
75. Which statement best describes semiconservative DNA replication?
Semiconservative replication produces DNA molecules with one parental strand and one newly synthesized strand.
Tip: “One old + one new” = semiconservative.
76. What is the function of primase during DNA replication?
Primase synthesizes short RNA primers that provide a starting point for DNA polymerase on both leading and lagging strands.
Tip: Primase = “starter RNA maker.”
77. Which of the following correctly describes the central dogma of molecular biology?
The central dogma states that genetic information flows from DNA to RNA (transcription) and then to protein (translation).
Tip: Central dogma = “DNA speaks in RNA, which builds protein.”
78. Which of the following is a stop codon in mRNA?
UAA is a stop codon, signaling termination of translation. Other stop codons are UAG and UGA.
Tip: Stop codons = “translation brakes.”
79. Which enzyme removes RNA primers and replaces them with DNA nucleotides?
DNA polymerase I removes RNA primers and fills in DNA nucleotides on the lagging strand.
Tip: DNA pol I = “primer replacement specialist.”
80. Which of the following is true about prokaryotic mRNA?
Prokaryotic mRNA is often polycistronic (encoding multiple proteins) and does not have a 5’ cap or poly-A tail.
Tip: Prokaryotic mRNA = “simple, multi-gene, no cap.”
81. Which of the following describes the function of rRNA?
rRNA combines with proteins to form ribosomes and catalyzes peptide bond formation during translation.
Tip: rRNA = “ribosome scaffold + catalyst.”
82. Which of the following best describes a genome?
The genome is the complete set of DNA, including all genes, in an organism.
Tip: Genome = “all the DNA blueprints.”
83. Which of the following best defines a mutation?
A mutation is a permanent alteration in the DNA sequence that may affect function.
Tip: Mutation = “permanent DNA change.”
84. Which of the following best explains why RNA uses uracil instead of thymine?
RNA is generally short-lived, and uracil is energetically cheaper than thymine to synthesize.
Tip: RNA = “economical and temporary; uses U.”
85. Which of the following statements is true about DNA replication fidelity?
DNA polymerase has 3’→5’ exonuclease activity that proofreads newly synthesized DNA to maintain high fidelity.
Tip: DNA polymerase = “master editor of replication.”
86. Which process produces two identical DNA molecules from one original molecule?
DNA replication duplicates the DNA to produce two identical molecules, each with one original strand and one new strand.
Tip: Replication = “copy the entire blueprint.”
87. Which of the following is NOT a component of a nucleotide?
Nucleotides are composed of a sugar, phosphate, and nitrogenous base. Amino acids are building blocks of proteins, not nucleotides.
Tip: Nucleotide ≠ amino acid; nucleic acid vs protein.
88. Which strand is synthesized continuously during DNA replication?
The leading strand is synthesized continuously toward the replication fork. The lagging strand is synthesized in fragments.
Tip: Leading = “go with the fork.”
89. Which of the following correctly matches the enzyme to its function?
Ligase seals gaps in the sugar-phosphate backbone between Okazaki fragments.
90. Which of the following best describes a codon?
A codon is a sequence of three nucleotides on mRNA that specifies a single amino acid.
Tip: Codon = “3-letter word in RNA.”
91. Which of the following statements about Okazaki fragments is correct?
Okazaki fragments are short segments of DNA synthesized discontinuously on the lagging strand.
Tip: Okazaki = “lagging, fragmented, stitched together.”
92. Which of the following is true about semiconservative replication?
Each replicated DNA molecule contains one original (parental) strand and one newly synthesized strand.
Tip: “Semiconservative = one old + one new.”
93. Which of the following is a function of the 5’ cap on eukaryotic mRNA?
The 5’ cap stabilizes mRNA and helps ribosomes recognize it for translation.
Tip: Cap = “mRNA helmet + ribosome flag.”
94. Which of the following best describes a point mutation?
A point mutation changes one nucleotide, potentially altering a single amino acid in a protein.
Tip: Point mutation = “single letter typo in DNA.”
95. Which enzyme synthesizes the majority of DNA on the leading strand in prokaryotes?
DNA polymerase III synthesizes most of the DNA on the leading strand continuously in prokaryotes.
Tip: DNA pol III = “main DNA builder.”
96. Which process converts the genetic code from RNA into a sequence of amino acids?
Translation decodes mRNA into a specific sequence of amino acids, forming a polypeptide chain.
97. Which of the following describes an operon in prokaryotes?
An operon is a group of genes regulated together by one promoter, common in prokaryotes.
Tip: Operon = “gene cluster under one switch.”
98. Which of the following is a pyrimidine?
Pyrimidines have a single-ring structure; thymine (T), cytosine (C), and uracil (U) are pyrimidines. Adenine and guanine are purines.
Tip: Pyrimidine = “single ring; T, C, U.”
99. Which of the following statements about eukaryotic transcription is correct?
Eukaryotic transcription in the nucleus produces various RNAs: mRNA, tRNA, and rRNA.
Tip: Transcription = “DNA → RNA types.”
100. Which of the following correctly pairs a type of RNA with its main function?
tRNA carries amino acids to the ribosome during translation. mRNA carries the code; rRNA forms ribosome; snRNA is for splicing.
Tip: tRNA = “delivery truck for amino acids.”
