NCERT BOOK CLASS 12TH BIOLOGY MCQ
Chapter 4 : Principle of Inheritance and Variation
Important Multiple Choice Question (MCQs)
1. Which plant did Mendel select for his experiments?
a) Wheat
b) Pea
c) Rice
d) Maize
Answer: b) Pea
2. Who discovered genes?
a) Gregor Mendel
b) Charles Darwin
c) T.H. Morgan
d) Watson and Crick
Answer: a) Gregor Mendel
3. What type of traits appear in the F1 hybrid generation?
a) Only dominant
b) Only recessive
c) Both dominant and recessive
d) None
Answer: a) Only dominant
4. Which of Mendel’s laws states that genes for different traits assort independently?
a) Law of Dominance
b) Law of Segregation
c) Law of Independent Assortment
d) Law of Mutation
Answer: c) Law of Independent Assortment
5. Sex-linked disorders are located on which chromosome?
a) Autosome
b) X chromosome
c) Y chromosome
d) Mitochondrial DNA
Answer: b) X chromosome
6. Haemophilia is what type of disorder?
a) Autosomal dominant
b) Autosomal recessive
c) X-linked dominant
d) X-linked recessive
Answer: d) X-linked recessive
7. How is sex determined in humans?
a) XX – Male, XY – Female
b) XX – Female, XY – Male
c) ZZ – Male, ZW – Female
d) None
Answer: b) XX – Female, XY – Male
8. What is the difference between genotype and phenotype?
a) Genotype is genetic makeup, phenotype is physical traits
b) Genotype is physical traits, phenotype is genetic makeup
c) Both are the same
d) None
Answer: a) Genotype is genetic makeup, phenotype is physical traits
9. Down syndrome is caused by:
a) Trisomy of chromosome 21
b) Absence of X chromosome
c) Extra Y chromosome
d) Autosomal mutation
Answer: a) Trisomy of chromosome 21
10. An example of polygenic inheritance is:
a) Yellow and green pea color
b) Human skin color
c) Blood group
d) Haemophilia
Answer: b) Human skin color
11. The ABO blood group system shows which type of inheritance?
a) Incomplete dominance
b) Co-dominance
c) Pleiotropy
d) Polygenic inheritance
Answer: b) Co-dominance
12. Mitochondrial inheritance is seen in:
a) Only males
b) Only females
c) From mother to offspring
d) From father to offspring
Answer: c) From mother to offspring
13. What is the chromosomal combination in Turner syndrome?
a) 44 + XXY
b) 44 + XO
c) 44 + XXX
d) 44 + XX
Answer: b) 44 + XO
14. What is the chromosomal combination in Klinefelter syndrome?
a) 44 + XXY
b) 44 + XO
c) 44 + XXX
d) 44 + XY
Answer: a) 44 + XXY
15. What is used for gene mapping?
a) Recombinant DNA technology
b) PCR
c) Genome sequencing
d) All of the above
Answer: d) All of the above
16. Gene therapy is used to treat:
a) Infectious diseases
b) Genetic disorders
c) Cancer
d) Both b and c
Answer: d) Both b and c
17. What does pedigree analysis show?
a) Inheritance of diseases in a family
b) DNA structure
c) Gene expression
d) Protein synthesis
Answer: a) Inheritance of diseases in a family
18. Phenylketonuria (PKU) is what type of disorder?
a) Autosomal dominant
b) Autosomal recessive
c) X-linked
d) Mitochondrial
Answer: b) Autosomal recessive
19. What is a mutation?
a) Change in DNA
b) Change in protein
c) Change in RNA
d) Change in cell division
Answer: a) Change in DNA
20. Sickle cell anemia is caused by which type of mutation?
a) Point mutation
b) Translocation
c) Deletion
d) Inversion
Answer: a) Point mutation
21. How many traits did Mendel study in his experiments?
a) 5
b) 7
c) 10
d) 12
Answer: b) 7
22. In pea plants, the gene for purple flowers (PP or Pp) is:
a) Dominant
b) Recessive
c) Co-dominant
d) Incompletely dominant
Answer: a) Dominant
23. In pea plants, the gene for white flowers (pp) is:
a) Dominant
b) Recessive
c) Co-dominant
d) Incompletely dominant
Answer: b) Recessive
24. If two heterozygous (Pp) plants are crossed, what is the phenotypic ratio in the F2 generation?
a) 1:1
b) 3:1
c) 1:2:1
d) 9:3:3:1
Answer: b) 3:1
25. What is the phenotypic ratio in a dihybrid cross (F2 generation)?
a) 9:3:3:1
b) 3:1
c) 1:2:1
d) 1:1:1:1
Answer: a) 9:3:3:1
26. What is the purpose of a test cross?
a) To determine genotype
b) To observe phenotype
c) To analyze DNA structure
d) To study protein structure
Answer: a) To determine genotype
27. What is the genotype for blood group ‘O’ in humans?
a) IAIA
b) IBIB
c) IAIB
d) ii
Answer: d) ii
28. What is the genotype for blood group ‘AB’ in humans?
a) IAIA
b) IBIB
c) IAIB
d) ii
Answer: c) IAIB
29. How is color blindness inherited?
a) Autosomal dominant
b) Autosomal recessive
c) X-linked dominant
d) X-linked recessive
Answer: d) X-linked recessive
30. If a woman is a carrier for color blindness, what is the probability her son will have the disorder?
a) 0%
b) 25%
c) 50%
d) 100%
Answer: c) 50%
31. What is a gene pool?
a) All genes of an organism
b) All genes in a population
c) All genes in a cell
d) All genes on a chromosome
Answer: b) All genes in a population
32. What is gene flow?
a) Transfer of genes between populations
b) Mutation in genes
c) Recombination of genes
d) Deletion of genes
Answer: a) Transfer of genes between populations
33. What is genetic drift?
a) Random change in gene frequency
b) Natural selection
c) Gene flow
d) Mutation
Answer: a) Random change in gene frequency
34. Who proposed the theory of natural selection?
a) Gregor Mendel
b) Charles Darwin
c) Lamarck
d) Hardy-Weinberg
Answer: b) Charles Darwin
35. What does the Hardy-Weinberg principle relate to?
a) Gene frequency stability
b) Mutation
c) Gene flow
d) Natural selection
Answer: a) Gene frequency stability
36. What is the Hardy-Weinberg equation?
a) p + q = 1
b) p² + 2pq + q² = 1
c) p + q = 0
d) p² + q² = 1
Answer: b) p² + 2pq + q² = 1
37. Albinism is what type of disorder?
a) Autosomal dominant
b) Autosomal recessive
c) X-linked
d) Mitochondrial
Answer: b) Autosomal recessive
38. Thalassemia is what type of disorder?
a) Autosomal dominant
b) Autosomal recessive
c) X-linked
d) Mitochondrial
Answer: b) Autosomal recessive
39. Cystic fibrosis is what type of disorder?
a) Autosomal dominant
b) Autosomal recessive
c) X-linked
d) Mitochondrial
Answer: b) Autosomal recessive
40. What is gene cloning?
a) Making multiple copies of a gene
b) Removing a gene
c) Altering a gene
d) Silencing a gene
Answer: a) Making multiple copies of a gene
41. What is DNA fingerprinting based on?
a) VNTR (Variable Number Tandem Repeats)
b) mRNA
c) tRNA
d) rRNA
Answer: a) VNTR
42. What is a genome?
a) Complete DNA of an organism
b) Complete RNA of an organism
c) Complete proteins of an organism
d) Complete cell cytoplasm
Answer: a) Complete DNA of an organism
43. What was the goal of the Human Genome Project?
a) Sequencing human DNA
b) Sequencing human RNA
c) Sequencing human proteins
d) Counting human cells
Answer: a) Sequencing human DNA
44. What technique uses gene splicing?
a) Recombinant DNA technology
b) PCR
c) DNA fingerprinting
d) Gene therapy
Answer: a) Recombinant DNA technology
45. What are transgenic plants?
a) Plants with foreign genes inserted
b) Plants with no genes
c) Plants with only natural genes
d) Plants with mutated genes
Answer: a) Plants with foreign genes inserted
46. What is Bt cotton?
a) Insect-resistant cotton
b) Disease-resistant cotton
c) Drought-resistant cotton
d) High-yield cotton
Answer: a) Insect-resistant cotton
47. What is Golden Rice?
a) Vitamin A-enriched rice
b) Vitamin C-enriched rice
c) Protein-enriched rice
d) Iron-enriched rice
Answer: a) Vitamin A-enriched rice
48. What is important for biodiversity conservation?
a) Gene banks
b) Seed banks
c) Botanical gardens
d) All of the above
Answer: d) All of the above
49. What is used for biofuel production?
a) Biomass
b) Fossil fuels
c) Nuclear energy
d) Solar energy
Answer: a) Biomass
50. Where is biotechnology applied?
a) Medicine
b) Agriculture
c) Environmental protection
d) All of the above
Answer: d) All of the above
51. What is the genotypic ratio in a monohybrid cross (F2 generation)?
a) 3:1
b) 1:2:1
c) 9:3:3:1
d) 1:1
Answer: b) 1:2:1
52. Mendel’s observation that yellow seeds are dominant over green seeds illustrates which law?
a) Law of Segregation
b) Law of Dominance
c) Law of Independent Assortment
d) Law of Mutation
Answer: b) Law of Dominance
53. If two heterozygous organisms are crossed, what is the probability of the dominant trait appearing in F1?
a) 25%
b) 50%
c) 75%
d) 100%
Answer: c) 75%
54. What is epistasis?
a) One gene affects the expression of another
b) Independent assortment of genes
c) Gene mutation
d) Gene flow
Answer: a) One gene affects the expression of another
55. How is sex determined in humans?
a) Autosomes
b) X chromosome
c) Y chromosome
d) Both X and Y chromosomes
Answer: d) Both X and Y chromosomes
56. Which disorder causes elongated limbs?
a) Down syndrome
b) Turner syndrome
c) Marfan syndrome
d) Klinefelter syndrome
Answer: c) Marfan syndrome
57. What is chromosomal aberration?
a) Change in chromosome structure/number
b) DNA breakage
c) Gene mutation
d) Protein synthesis error
Answer: a) Change in chromosome structure/number
58. What is gene duplication?
a) Creation of extra gene copies
b) Gene deletion
c) Gene breakage
d) Gene transfer
Answer: a) Creation of extra gene copies
59. What is gene expression?
a) Process of making proteins from genes
b) Gene mutation
c) Gene recombination
d) Gene deletion
Answer: a) Process of making proteins from genes
60. What is pleiotropy?
a) One gene influences multiple traits
b) Multiple genes influence one trait
c) Independent gene assortment
d) Gene mutation
Answer: a) One gene influences multiple traits
61. How many autosomes do humans have?
a) 22 pairs
b) 23 pairs
c) 44 pairs
d) 46 pairs
Answer: a) 22 pairs
62. What can gene mutations cause?
a) Genetic disorders
b) Cancer
c) Both a and b
d) Neither
Answer: c) Both a and b
63. In sickle cell anemia, which part of hemoglobin is altered?
a) Alpha chain
b) Beta chain
c) Gamma chain
d) Delta chain
Answer: b) Beta chain
64. Huntington’s disease is what type of disorder?
a) Autosomal dominant
b) Autosomal recessive
c) X-linked
d) Mitochondrial
Answer: a) Autosomal dominant
65. Which technology is used for gene editing?
a) CRISPR-Cas9
b) PCR
c) DNA fingerprinting
d) Gene cloning
Answer: a) CRISPR-Cas9
66. What is genomic imprinting?
a) Gene expression depends on parental origin
b) Gene mutation
c) Gene recombination
d) Gene deletion
Answer: a) Gene expression depends on parental origin
67. How is mitochondrial DNA inherited?
a) Only from the mother
b) Only from the father
c) From both parents
d) Not inherited
Answer: a) Only from the mother
68. What is a frameshift mutation?
a) Insertion/deletion of nucleotides
b) Single base change
c) DNA breakage
d) DNA duplication
Answer: a) Insertion/deletion of nucleotides
69. What is trisomy?
a) Extra copy of a chromosome
b) Missing chromosome
c) Broken chromosome
d) Duplicated chromosome
Answer: a) Extra copy of a chromosome
70. What is monosomy?
a) Missing chromosome
b) Extra chromosome
c) Broken chromosome
d) Duplicated chromosome
Answer: a) Missing chromosome
71. What is used in gene therapy?
a) Viruses
b) Bacteria
c) Fungi
d) Protozoa
Answer: a) Viruses
72. What is gene silencing?
a) Blocking gene expression
b) Activating genes
c) Deleting genes
d) Duplicating genes
Answer: a) Blocking gene expression
73. What is a genomic library?
a) Collection of DNA fragments
b) Collection of RNA
c) Collection of proteins
d) Collection of cells
Answer: a) Collection of DNA fragments
74. What is a gene probe?
a) Known DNA sequence
b) Known RNA sequence
c) Known protein sequence
d) Known cell sequence
Answer: a) Known DNA sequence
75. What is used for gene mapping?
a) Marker genes
b) Restriction enzymes
c) PCR
d) All of the above
Answer: d) All of the above