🧬 Principles of Inheritance and Variation

MCQ NEET + Board Level

1. Father of Genetics is:

A) Darwin
B) Mendel
C) Morgan
D) Lamarck

✅ Answer: B) Mendel

2. Mendel conducted experiments on:

A) Maize B) Pea Plant C) Wheat D) Rice

✅ Answer: B) Pea Plant

3. Scientific name of pea plant is:

A) Pisum sativum B) Zea mays C) Oryza sativa D) Triticum aestivum

✅ Answer: A) Pisum sativum

4. Which trait is dominant in pea?

A) Wrinkled seed B) Green seed C) Tall plant D) White flower

✅ Answer: C) Tall plant

5. Which trait is recessive?

A) Tall B) Round seed C) Violet flower D) Dwarf

✅ Answer:

D) Dwarf

6. Mendel's Law of Segregation is also called:

A) Purity of gametes B) Independent assortment C) Dominance D) Linkage

✅ Answer: A) Purity of gametes

7. Genotype of pure tall plant:

A) Tt B) tt C) TT D) TTT

✅ Answer: C) TT

8. Genotype of hybrid tall plant:

A) TT B) Tt C) tt D) TTT

✅ Answer: B) Tt

9. Phenotypic ratio in monohybrid cross:

A) 1:2:1 B) 3:1 C) 9:3:3:1 D) 1:1

✅ Answer: B) 3:1

10. Genotypic ratio in monohybrid cross:

A) 1:2:1 B) 3:1 C) 1:1 D) 9:3:3:1

✅ Answer: A) 1:2:1

11. Test cross means:

A) TT × TT B) Tt × TT C) Tt × tt D) TT × tt

✅ Answer: C) Tt × tt

12. Dihybrid phenotypic ratio:

A) 3:1 B) 1:2:1 C) 9:3:3:1 D) 1:1

✅ Answer: C) 9:3:3:1

13. Law of Independent Assortment is based on:

A) Monohybrid cross B) Dihybrid cross C) Back cross D) Mutation

✅ Answer: B) Dihybrid cross

14. Alternative forms of a gene are called:

A) Chromosomes B) Alleles C) Loci D) Traits

✅ Answer: B) Alleles

15. Position of gene on chromosome:

A) Locus B) Trait C) Allele D) Factor

✅ Answer: A) Locus

16. Phenotype means:

A) Genetic constitution B) Physical appearance C) Gene pair D) DNA sequence

✅ Answer: B) Physical appearance

17. Genotype means:

A) Appearance B) Environment C) Genetic constitution D) Mutation

✅ Answer: C) Genetic constitution

18. Incomplete dominance was discovered in:

A) Pea B) Snapdragon C) Maize D) Drosophila

✅ Answer: B) Snapdragon

19. Phenotypic ratio in incomplete dominance:

A) 3:1 B) 1:2:1 C) 9:3:3:1 D) 1:1

✅ Answer: B) 1:2:1

20. Example of codominance:

A) Flower colour B) Height C) ABO blood group D) Seed shape

✅ Answer: C) ABO blood group

21. IA and IB alleles show:

A) Dominance B) Codominance C) Linkage D) Mutation

✅ Answer: B) Codominance

22. Total alleles controlling ABO blood group:

A) 2 B) 3 C) 4 D) 5

✅ Answer: B) 3

23. Universal donor:

A) A B) B C) AB D) O

✅ Answer: D) O

24. Universal recipient:

A) O B) A C) B D) AB

✅ Answer: D) AB

25. Blood group AB has genotype:

A) IAIA B) IBIB C) IAIB D) ii

✅ Answer: C) IAIB

🔥 NEET Important Topics Covered

✔ Mendel
✔ Monohybrid Cross
✔ Dihybrid Cross
✔ Test Cross
✔ Dominance
✔ Incomplete Dominance
✔ Codominance
✔ ABO Blood Group

🧬 Principles of Inheritance and Variation

MCQ Set–2 (Q26–Q50) | NEET + Board PYQ Level

26. ABO blood group system was discovered by:

A) Mendel

B) Morgan

C) Landsteiner

D) Watson

✅ Answer: C) Landsteiner

---

27. A person with genotype IAi has blood group:

A) A

B) B

C) AB

D) O

✅ Answer: A) A

---

28. A person with genotype IBi has blood group:

A) A

B) B

C) AB

D) O

✅ Answer: B) B

---

29. Multiple alleles are present in:

A) One chromosome

B) One population

C) One individual

D) One gamete

✅ Answer: B) One population

---

30. Number of genotypes in ABO blood group:

A) 3

B) 4

C) 6

D) 8

✅ Answer: C) 6

---

31. Chromosomal Theory of Inheritance was proposed by:

A) Darwin and Lamarck

B) Sutton and Boveri

C) Watson and Crick

D) Mendel and Morgan

✅ Answer: B) Sutton and Boveri

---

32. Genes are located on:

A) Ribosomes

B) Lysosomes

C) Chromosomes

D) Golgi bodies

✅ Answer: C) Chromosomes

---

33. Experimental proof of chromosomal theory was given by:

A) Mendel

B) Darwin

C) Morgan

D) Haldane

✅ Answer: C) Morgan

---

34. Morgan worked on:

A) Pea plant

B) Drosophila

C) Wheat

D) Rice

✅ Answer: B) Drosophila

---

35. Drosophila is:

A) Mosquito

B) Housefly

C) Fruit Fly

D) Butterfly

✅ Answer: C) Fruit Fly

---

36. Linkage refers to:

A) Mutation of genes

B) Genes on same chromosome inherited together

C) Crossing over

D) Recombination

✅ Answer: B)

---

37. Crossing over occurs during:

A) Prophase I

B) Metaphase I

C) Anaphase I

D) Telophase I

✅ Answer: A) Prophase I

---

38. Exchange of chromosomal segments leads to:

A) Mutation

B) Recombination

C) Replication

D) Translation

✅ Answer: B) Recombination

---

39. Recombination increases:

A) Similarity

B) Variation

C) Extinction

D) Mutation rate

✅ Answer: B) Variation

---

40. XX chromosomes are found in:

A) Human male

B) Human female

C) Male bird

D) Male grasshopper

✅ Answer: B) Human female

---

41. Human male chromosome constitution:

A) XX

B) XY

C) XO

D) YY

✅ Answer: B) XY

---

42. Sex of child is determined by:

A) Mother

B) Father

C) Both equally

D) Environment

✅ Answer: B) Father

---

43. Which chromosome carries SRY gene?

A) X chromosome

B) Y chromosome

C) Chromosome 21

D) Chromosome 22

✅ Answer: B) Y chromosome

---

44. Human female produces:

A) X and Y gametes

B) Only X gametes

C) Only Y gametes

D) XY gametes

✅ Answer: B) Only X gametes

---

45. Human male produces:

A) Only X sperm

B) Only Y sperm

C) X and Y sperm

D) XY sperm

✅ Answer: C) X and Y sperm

---

46. Haemophilia is:

A) Autosomal dominant

B) X-linked recessive

C) Y-linked

D) Codominant

✅ Answer: B)

---

47. Colour blindness is:

A) X-linked recessive

B) Y-linked

C) Autosomal dominant

D) Codominant

✅ Answer: A)

---

48. Pedigree analysis is used to study:

A) Evolution

B) Inheritance pattern in families

C) DNA replication

D) Mutation only

✅ Answer: B)

---

49. Pedigree chart uses:

A) Squares and circles

B) Triangles only

C) Lines only

D) Arrows only

✅ Answer: A)

---

50. Affected male in pedigree is represented by:

A) Shaded circle

B) Unshaded square

C) Shaded square

D) Triangle

✅ Answer: C)

🔥 NEET Most Repeated Topics Covered

✔ Multiple Alleles

✔ ABO Blood Group

✔ Chromosomal Theory

✔ Morgan's Experiments

Mendelian Disorders

✔ Haemophilia
✔ Colour Blindness
✔ Sickle Cell Anaemia
✔ Thalassemia

Chromosomal Disorders

✔ Down Syndrome (47, +21)
✔ Klinefelter Syndrome (47, XXY)
✔ Turner Syndrome (45, XO)

Most Repeated NEET Fact 🚨

Down Syndrome → Trisomy 21
Turner Syndrome → XO Female
Klinefelter Syndrome → XXY Male
Sickle Cell Anaemia → Glutamic Acid → Valine substitution
76. Mendel selected pea plant because:

A) Long life cycle B) Easily available contrasting traits C) Difficult cultivation D) Large chromosome number

✅ B

77. Number of contrasting characters studied by Mendel:

A) 5 B) 6 C) 7 D) 8

✅ C

78. A cross between F₁ and recessive parent is:

A) Back cross B) Test cross C) Monohybrid cross D) Dihybrid cross

✅ B

79. All test crosses are:

A) Back crosses B) Monohybrid crosses C) Dihybrid crosses D) Self crosses

✅ A

80. Incomplete dominance was first observed in:

A) Snapdragon B) Pea C) Maize D) Drosophila

✅ A

81. ABO blood group is controlled by:

A) 2 alleles B) 3 alleles C) 4 alleles D) 5 alleles

✅ B

82. IA and IB alleles are:

A) Recessive B) Codominant C) Linked D) Lethal

✅ B

83. Gene interaction where one gene affects multiple traits:

A) Polygenic inheritance B) Pleiotropy C) Linkage D) Codominance

✅ B

84. Example of pleiotropy:

A) Sickle-cell anaemia B) Colour blindness C) Haemophilia D) Turner syndrome

✅ A

85. Linkage was discovered by:

A) Mendel B) Morgan C) Darwin D) Bateson

✅ B

86. Recombination frequency is highest when genes are:

A) Closely linked B) Far apart C) Identical D) Dominant

✅ B

87. Crossing over occurs between:

A) Sister chromatids B) Non-homologous chromosomes C) Homologous chromosomes D) Ribosomes

✅ C

88. Sex-linked genes are located on:

A) Autosomes B) Sex chromosomes C) Mitochondria D) Ribosomes

✅ B

89. Human female produces:

A) X gametes only B) Y gametes only C) X and Y D) XY

✅ A

90. Human male produces:

A) Only X B) Only Y C) Both X and Y D) XY sperm

✅ C

91. Which disorder is sex-linked?

A) Down syndrome B) Haemophilia C) Turner syndrome D) Klinefelter syndrome

✅ B

92. Colour blindness mainly affects:

A) Females B) Males C) Both equally D) Plants

✅ B

93. Pedigree analysis helps study:

A) Evolution B) Inheritance pattern C) Ecology D) Taxonomy

✅ B

94. Nondisjunction occurs during:

A) Cell division B) Respiration C) Translation D) Replication

✅ A

95. Trisomy means:

A) Loss of chromosome B) Extra chromosome C) Mutation D) Crossing over

✅ B

96. Monosomy means:

A) Extra chromosome B) Missing chromosome C) Polyploidy D) Mutation

✅ B

97. Turner syndrome is:

A) Trisomy B) Monosomy X C) XXY D) XYY

✅ B

98. Klinefelter syndrome individuals are:

A) XO females B) XXY males C) XYY males D) XXX females

✅ B

99. Chromosomal disorders arise due to:

A) Gene mutation only B) Change in chromosome number C) Nutrition D) Infection

✅ B

100. Father of Experimental Genetics:

A) Darwin B) Mendel C) Morgan D) Lamarck

✅ B

MCQ Set–5 (Q101–Q125) | High Yield NEET

101. Law of Dominance explains:

A) F₂ generation B) Expression of dominant allele in F₁ C) Mutation D) Linkage

✅ B

102. Law of Segregation is based on:

A) Separation of alleles during gamete formation B) Mutation C) Linkage D) Crossing over

✅ A

103. Pure line means:

A) Heterozygous B) Homozygous C) Hybrid D) Recombinant

✅ B

104. TT × tt gives:

A) TT B) tt C) All Tt D) 1:1

✅ C

105. F₂ ratio in dihybrid cross:

A) 3:1 B) 1:2:1 C) 9:3:3:1 D) 1:1

✅ C

106. Independent assortment occurs due to:

A) Random arrangement of chromosomes B) Mutation C) Linkage D) Replication

✅ A

107. Linkage reduces:

A) Similarity B) Recombination C) Mutation D) Dominance

✅ B

108. Recombination produces:

A) Variability B) Uniformity C) Clones D) Extinction

✅ A

109. Morgan used which organism?

A) Pisum B) Drosophila C) Maize D) Rice

✅ B

110. Drosophila has chromosome number:

A) 4 pairs B) 8 pairs C) 23 pairs D) 2 pairs

✅ A

111–125 Important Rapid Fire
1. ABO blood group → Multiple alleles ✅
2. IA and IB → Codominant ✅
3. ii genotype → Blood group O ✅
4. Universal donor → O ✅
5. Universal recipient → AB ✅
6. Haemophilia → X-linked recessive ✅
7. Colour blindness → X-linked recessive ✅
8. Down syndrome → Trisomy 21 ✅
9. Turner syndrome → XO ✅
10. Klinefelter syndrome → XXY ✅
11. Sickle-cell anaemia → Autosomal recessive ✅
12. Mutation in β-globin gene → Sickle cell ✅
13. Sutton & Boveri → Chromosomal theory ✅
14. Morgan → Linkage ✅
15. Mendel → Father of Genetics ✅
MCQ Set–6 (Q126–Q150) | NEET Revision Capsule
1. First filial generation = F₁ ✅
2. Second filial generation = F₂ ✅
3. Hybrid = Heterozygous ✅
4. Pure tall genotype = TT ✅
5. Dwarf genotype = tt ✅
6. Test cross ratio = 1:1 ✅
7. Monohybrid phenotype ratio = 3:1 ✅
8. Monohybrid genotype ratio = 1:2:1 ✅
9. Dihybrid phenotype ratio = 9:3:3:1 ✅
10. Dihybrid genotype ratio = 1:2:1:2:4:2:1:2:1 ✅
11. Gene position = Locus ✅
12. Alternative form of gene = Allele ✅
13. Physical appearance = Phenotype ✅
14. Genetic makeup = Genotype ✅
15. Study of heredity = Genetics ✅
16. Sex determination in humans = XX-XY type ✅
17. SRY gene present on = Y chromosome ✅
18. Human chromosome number = 46 ✅
19. Autosomes in humans = 44 ✅
20. Sex chromosomes = 2 ✅
21. Female sex chromosomes = XX ✅
22. Male sex chromosomes = XY ✅
23. Crossing over occurs in = Prophase I ✅
24. Evolutionary raw material = Variation ✅
25. Most important unit of inheritance = Gene
26. 151. Mendel published his work in:
  
  A) 1859
  B) 1865
  C) 1900
  D) 1910
  
  ✅ B
  
  152. Rediscovery of Mendel's work was done by:
  
  A) Darwin, Lamarck, Morgan B) De Vries, Correns, Tschermak C) Watson, Crick, Wilkins D) Sutton, Boveri, Morgan
  
  ✅ B
  
  153. Which law is called Law of Purity of Gametes?
  
  A) Dominance B) Segregation C) Linkage D) Codominance
  
  ✅ B
  
  154. A homozygous dominant genotype is:
  
  A) Tt B) tt C) TT D) TTT
  
  ✅ C
  
  155. In a monohybrid cross, recessive trait reappears in:
  
  A) P generation B) F₁ generation C) F₂ generation D) Gametes
  
  ✅ C
  
  156. Which blood group has no antigen?
  
  A) A B) B C) AB D) O
  
  ✅ D
  
  157. Which blood group has both antigens?
  
  A) A B) B C) AB D) O
  
  ✅ C
  
  158. Which chromosome determines maleness in humans?
  
  A) X B) Y C) 21 D) 22
  
  ✅ B
  
  159. Sex-linked inheritance was discovered by:
  
  A) Mendel B) Morgan C) Darwin D) Bateson
  
  ✅ B
  
  160. Haemophilia is more common in:
  
  A) Females B) Males C) Both equally D) Plants
  
  ✅ B
  
  161. Carrier female genotype for haemophilia:
  
  A) XʰXʰ B) XᴴXᴴ C) XᴴXʰ D) XʰY
  
  ✅ C
  
  162. Colour blindness affects:
  
  A) Retina B) Colour vision C) Hearing D) Growth
  
  ✅ B
  
  163. Sickle-cell anaemia is due to:
  
  A) Chromosomal mutation B) Point mutation C) Polyploidy D) Deletion
  
  ✅ B
  
  164. Down syndrome individuals have:
  
  A) 45 chromosomes B) 46 chromosomes C) 47 chromosomes D) 48 chromosomes
  
  ✅ C
  
  165. Turner syndrome is:
  
  A) XO female B) XXY male C) Trisomy 21 D) XYY male
  
  ✅ A
  
  166. Klinefelter syndrome is:
  
  A) XO B) XXY C) XXX D) XYY
  
  ✅ B
  
  167. Which disorder is due to trisomy?
  
  A) Turner syndrome B) Down syndrome C) Haemophilia D) Colour blindness
  
  ✅ B
  
  168. Pedigree analysis is useful for:
  
  A) Evolution B) Heredity study C) Ecology D) Anatomy
  
  ✅ B
  
  169. The unit of inheritance is:
  
  A) Chromosome B) DNA C) Gene D) Nucleus
  
  ✅ C
  
  170. Linkage refers to genes located on:
  
  A) Different chromosomes B) Same chromosome C) Ribosomes D) Mitochondria
  
  ✅ B
  
  171. Crossing over increases:
  
  A) Mutation B) Variation C) Similarity D) Extinction
  
  ✅ B
  
  172. Recombination occurs during:
  
  A) Mitosis B) Meiosis C) Binary fission D) Budding
  
  ✅ B
  
  173. Mendel's factors are now called:
  
  A) Chromosomes B) Genes C) DNA D) Alleles
  
  ✅ B
  
  174. ABO blood group inheritance shows:
  
  A) Incomplete dominance B) Codominance C) Linkage D) Mutation
  
  ✅ B
  
  175. Example of multiple alleles:
  
  A) Height B) ABO blood group C) Colour blindness D) Haemophilia
  
  ✅ B
  
  176. Father of Genetics:
  
  ✅ Mendel
  
  177. Father of Experimental Genetics:
  
  ✅ Mendel
  
  178. Chromosomal Theory:
  
  ✅ Sutton & Boveri
  
  179. Linkage discovered by:
  
  ✅ Morgan
  
  180. Fruit fly scientific name:
  
  ✅ Drosophila melanogaster
  
  181. Universal donor:
  
  ✅ O
  
  182. Universal recipient:
  
  ✅ AB
  
  183. Blood group O genotype:
  
  ✅ ii
  
  184. Blood group AB genotype:
  
  ✅ IAIB
  
  185. Law based on monohybrid cross:
  
  ✅ Segregation
  
  186. Law based on dihybrid cross:
  
  ✅ Independent Assortment
  
  187. Phenotypic ratio in monohybrid:
  
  ✅ 3:1
  
  188. Genotypic ratio in monohybrid:
  
  ✅ 1:2:1
  
  189. Phenotypic ratio in dihybrid:
  
  ✅ 9:3:3:1
  
  190. Crossing over stage:
  
  ✅ Pachytene (Prophase I)
  
  191. Human chromosome number:
  
  ✅ 46
  
  192. Human autosomes:
  
  ✅ 44
  
  193. Human sex chromosomes:
  
  ✅ 2
  
  194. Male chromosome constitution:
  
  ✅ XY
  
  195. Female chromosome constitution:
  
  ✅ XX
  
  196. Down syndrome:
  
  ✅ Trisomy 21
  
  197. Turner syndrome:
  
  ✅ XO
  
  198. Klinefelter syndrome:
  
  ✅ XXY
  
  199. Sickle-cell anaemia:
  
  ✅ Autosomal recessive disorder
  
  200. Most important NEET question:
  
  Who determines the sex of the child? ✅ Father (X or Y sperm)
  
  🎯 Chapter Complete (200 MCQs)
  
  Most Repeated NEET PYQ Topics
  
  ⭐ Mendel's Laws
  ⭐ Monohybrid & Dihybrid Cross
  ⭐ Test Cross
  ⭐ ABO Blood Group
  ⭐ Multiple Alleles
  ⭐ Codominance
  ⭐ Linkage & Recombination
  ⭐ Sex Determination
  ⭐ Pedigree Analysis
  ⭐ Haemophilia
  ⭐ Colour Blindness
  ⭐ Sickle Cell Anaemia
  ⭐ Thalassemia
  ⭐ Down Syndrome
  ⭐ Turner Syndrome
  ⭐ Klinefelter Syndrome
  
  These 200 questions cover the highest-yield NCERT and NEET areas of the chapter.
27. Today's motivation
28. NCERT ki kitaab hai talwar,
29. NEET ka maidaan hai taiyaar,
30. Neend ko keh de ab alvida,
31. Doctor banna hai abki baar.

class 12 principal of inheritance full notes