NCERT BOOK CLASS 12TH BIOLOGY MCQ
Chapter 5 : Molecular Basis of Inheritance
Important MCQs with Answers
1. What is the full form of DNA?
a) Deoxyribonucleic Acid
b) Dinitrogen Acid
c) Deoxyribose Nucleotide
d) Dinucleotide Acid
Answer: a) Deoxyribonucleic Acid
2. How many types of nitrogenous bases are present in DNA?
a) 2
b) 4
c) 5
d) 6
Answer: b) 4 (Adenine, Guanine, Cytosine, Thymine)
3. Which base replaces thymine (T) in RNA?
a) Adenine
b) Uracil
c) Guanine
d) Cytosine
Answer: b) Uracil
4. Who proposed the double-helix model of DNA?
a) Gregor Mendel
b) Watson and Crick
c) Charles Darwin
d) Louis Pasteur
Answer: b) Watson and Crick
5. What type of sugar is present in DNA?
a) Glucose
b) Fructose
c) Deoxyribose
d) Ribose
Answer: c) Deoxyribose
6. How does DNA replication occur?
a) Conservative
b) Semi-conservative
c) Dispersive
d) Random
Answer: b) Semi-conservative
7. Which enzyme is responsible for DNA replication?
a) Pepsin
b) DNA Polymerase
c) Amylase
d) Lipase
Answer: b) DNA Polymerase
8. What is produced during transcription?
a) DNA
b) RNA
c) Protein
d) Lipid
Answer: b) RNA
9. Which RNA carries the code for protein synthesis?
a) mRNA (Messenger RNA)
b) tRNA (Transfer RNA)
c) rRNA (Ribosomal RNA)
d) snRNA (Small Nuclear RNA)
Answer: a) mRNA
10. How many codons are there in the genetic code?
a) 20
b) 64
c) 16
d) 32
Answer: b) 64
11. How many nucleotides make up a codon?
a) 1
b) 2
c) 3
d) 4
Answer: c) 3
12. Where does translation occur?
a) Nucleus
b) Ribosome
c) Mitochondria
d) Golgi Apparatus
Answer: b) Ribosome
13. What was the goal of the Human Genome Project?
a) Sequencing human DNA
b) Developing new drugs
c) Creating GM crops
d) Studying fossils
Answer: a) Sequencing human DNA
14. Which technique is used in DNA fingerprinting?
a) PCR
b) X-Ray
c) Ultrasound
d) MRI
Answer: a) PCR
15. In which organism is the Lac Operon found?
a) Humans
b) E. coli
c) Yeast
d) Maize
Answer: b) E. coli
16. What is a mutation?
a) Change in DNA
b) Breakdown of protein
c) Cell division
d) Gene transfer
Answer: a) Change in DNA
17. Who discovered the operon?
a) Watson and Crick
b) Jacob and Monod
c) Mendel
d) Darwin
Answer: b) Jacob and Monod
18. In which process is a polypeptide chain synthesized?
a) Transcription
b) Translation
c) DNA replication
d) Mutation
Answer: b) Translation
19. What is the function of spliceosomes?
a) DNA replication
b) mRNA processing
c) Protein synthesis
d) Cell division
Answer: b) mRNA processing
20. Where do transcription and translation occur in prokaryotes?
a) Nucleus
b) Cytoplasm
c) Mitochondria
d) Ribosome
Answer: b) Cytoplasm
21. Where does transcription occur in eukaryotes?
a) Nucleus
b) Cytoplasm
c) Ribosome
d) Golgi Body
Answer: a) Nucleus
22. In DNA, the phosphate group is attached to what?
a) Nitrogen base
b) Sugar
c) Amino acid
d) Lipid
Answer: b) Sugar
23. How is the length of DNA measured?
a) Nanometer
b) Base pairs
c) Dalton
d) Grams
Answer: b) Base pairs
24. Which proteins are associated with DNA?
a) Histones
b) RNA
c) Lipids
d) Carbohydrates
Answer: a) Histones
25. A gene is a segment of what?
a) DNA
b) RNA
c) Protein
d) Lipid
Answer: a) DNA
26. What is PCR used for?
a) DNA replication
b) Protein synthesis
c) Cell division
d) Inducing mutations
Answer: a) DNA replication
27. What does the Central Dogma describe?
a) DNA → RNA → Protein
b) RNA → DNA → Protein
c) Protein → RNA → DNA
d) DNA → Protein → RNA
Answer: a) DNA → RNA → Protein
28. What are ribosomes made of?
a) rRNA and protein
b) Only DNA
c) Lipid
d) Carbohydrate
Answer: a) rRNA and protein
29. What is the function of tRNA?
a) Carries amino acids to ribosomes
b) Replicates DNA
c) Degrades mRNA
d) Breaks down proteins
Answer: a) Carries amino acids to ribosomes
30. What is the first step in protein synthesis?
a) Transcription
b) Translation
c) DNA replication
d) Mutation
Answer: a) Transcription
31. What is an intron?
a) Non-coding part of a gene
b) Coding part of a gene
c) Fragment of protein
d) Type of RNA
Answer: a) Non-coding part of a gene
32. What is an exon?
a) Coding part of a gene
b) Non-coding part of a gene
c) Part of DNA replication
d) Type of mutation
Answer: a) Coding part of a gene
33. What is the function of restriction enzymes?
a) Cuts DNA at specific sites
b) Breaks down proteins
c) Synthesizes RNA
d) Divides cells
Answer: a) Cuts DNA at specific sites
34. What is used in gene cloning?
a) Plasmid
b) Ribosome
c) Golgi body
d) Lysosome
Answer: a) Plasmid
35. What does DNA ligase do?
a) Joins DNA fragments
b) Cuts DNA
c) Makes RNA
d) Breaks proteins
Answer: a) Joins DNA fragments
36. What is gene therapy used for?
a) Treating genetic disorders
b) Treating infections
c) Treating cancer
d) All of the above
Answer: d) All of the above
37. What are transgenic organisms?
a) Organisms with foreign genes
b) Naturally mutated organisms
c) Organisms without genes
d) Found only in labs
Answer: a) Organisms with foreign genes
38. What is a genome?
a) Complete DNA of an organism
b) A protein
c) A cell
d) An organ
Answer: a) Complete DNA of an organism
39. How many chromosomes do humans have?
a) 23
b) 46
c) 64
d) 32
Answer: b) 46 (23 pairs)
40. During DNA replication, Okazaki fragments form in which strand?
a) Leading strand
b) Lagging strand
c) Both strands
d) RNA
Answer: b) Lagging strand
41. Which enzyme protects chromosome ends?
a) Telomerase
b) DNA polymerase
c) Ligase
d) Helicase
Answer: a) Telomerase
42. Which RNA is a component of ribosomes?
a) mRNA
b) tRNA
c) rRNA
d) snRNA
Answer: c) rRNA
43. What is a silent mutation?
a) DNA change with no effect on protein
b) DNA change altering protein
c) Complete DNA loss
d) RNA breakdown
Answer: a) DNA change with no effect on protein
44. What is a missense mutation?
a) DNA change altering amino acid
b) DNA change creating a stop codon
c) Gene duplication
d) Gene deletion
Answer: a) DNA change altering amino acid
45. What is a nonsense mutation?
a) DNA change creating a stop codon
b) DNA change altering amino acid
c) Gene duplication
d) Gene deletion
Answer: a) DNA change creating a stop codon
46. What causes a frameshift mutation?
a) Insertion or deletion of nucleotides
b) Gene duplication
c) DNA inversion
d) DNA translocation
Answer: a) Insertion or deletion of nucleotides
47. Who proved DNA is genetic material?
a) Gregor Mendel
b) Watson & Crick
c) Avery, MacLeod & McCarty
d) Charles Darwin
Answer: c) Avery, MacLeod & McCarty
48. What did Hershey & Chase use to prove DNA is genetic material?
a) Bacteriophage
b) Yeast
c) Maize
d) Humans
Answer: a) Bacteriophage
49. What is used in DNA fingerprinting?
a) VNTR (Variable Number Tandem Repeats)
b) mRNA
c) tRNA
d) rRNA
Answer: a) VNTR
50. Which technique studies gene expression?
a) PCR
b) DNA fingerprinting
c) Northern blotting
d) Electrophoresis
Answer: c) Northern blotting
51. What bond connects nucleotides in DNA?
a) Hydrogen bond
b) Phosphodiester bond
c) Peptide bond
d) Glycosidic bond
Answer: b) Phosphodiester bond
52. Which enzyme separates DNA strands during replication?
a) Helicase
b) DNA polymerase
c) Ligase
d) Primase
Answer: a) Helicase
53. Which enzyme synthesizes RNA primers in DNA replication?
a) Primase
b) DNA polymerase
c) Ligase
d) Helicase
Answer: a) Primase
54. In DNA, thymine pairs with?
a) Adenine
b) Guanine
c) Cytosine
d) Uracil
Answer: a) Adenine
55. What is the synthesis of RNA called?
a) Transcription
b) Translation
c) Replication
d) Transformation
Answer: a) Transcription
56. What is added to eukaryotic mRNA during processing?
a) Poly-A tail
b) Introns
c) Ribosomes
d) Histones
Answer: a) Poly-A tail
57. Which codon signals the start of protein synthesis?
a) AUG
b) UAA
c) UGA
d) UAG
Answer: a) AUG
58. Which codon signals the stop of protein synthesis?
a) UAA
b) AUG
c) UUU
d) CCC
Answer: a) UAA
59. What does tRNA’s anticodon bind to?
a) DNA codon
b) mRNA codon
c) rRNA codon
d) Protein codon
Answer: b) mRNA codon
60. In which organism are operons found?
a) Bacteria
b) Humans
c) Yeast
d) Plants
Answer: a) Bacteria
61. The Lac Operon is related to the metabolism of?
a) Lactose
b) Glucose
c) Fructose
d) Maltose
Answer: a) Lactose
62. Which DNA is used in DNA fingerprinting?
a) Non-coding DNA
b) Coding DNA
c) Mitochondrial DNA
d) Plasmid DNA
Answer: a) Non-coding DNA
63. Which technique separates DNA fragments?
a) Gel electrophoresis
b) PCR
c) Centrifugation
d) Chromatography
Answer: a) Gel electrophoresis
64. What is used in recombinant DNA technology?
a) Plasmid
b) Ribosome
c) Golgi body
d) Lysosome
Answer: a) Plasmid
65. Who developed PCR?
a) Kary Mullis
b) Watson & Crick
c) Gregor Mendel
d) Louis Pasteur
Answer: a) Kary Mullis
66. Approximately how many genes are in the human genome?
a) 20,000-25,000
b) 10,000
c) 50,000
d) 100,000
Answer: a) 20,000-25,000
67. Which DNA is used to study maternal lineage?
a) Mitochondrial DNA
b) Nuclear DNA
c) Plasmid DNA
d) Ribosomal DNA
Answer: a) Mitochondrial DNA
68. Which organism has circular DNA?
a) E. coli
b) Humans
c) Yeast
d) Maize
Answer: a) E. coli
69. What is chromatin made of?
a) DNA + Histones
b) RNA + Protein
c) Lipid + Carbohydrate
d) DNA + RNA
Answer: a) DNA + Histones
70. Where is DNA located in eukaryotes?
a) Nucleus
b) Cytoplasm
c) Ribosome
d) Golgi body
Answer: a) Nucleus
71. Which enzyme is involved in transcription?
a) RNA polymerase
b) DNA polymerase
c) Ligase
d) Helicase
Answer: a) RNA polymerase
72. How many subunits does prokaryotic RNA polymerase have?
a) 5
b) 1
c) 3
d) 10
Answer: a) 5
73. What are non-coding sequences in eukaryotic genes called?
a) Introns
b) Exons
c) Promoters
d) Terminators
Answer: a) Introns
74. What process removes introns?
a) Splicing
b) Transcription
c) Translation
d) Replication
Answer: a) Splicing
75. Which RNA carries amino acids during protein synthesis?
a) tRNA
b) mRNA
c) rRNA
d) snRNA
Answer: a) tRNA