1. Inheritance of two different characters together is known as

A. Monohybrid inheritance B. Polygenic inheritance C. Dihybrid inheritance D. Test cross

✅ Answer: C

📘 Explanation: Dihybrid inheritance involves two gene pairs controlling two traits.

2. Mendel studied dihybrid inheritance using which traits in pea plants?

A. Height and flower colour B. Pod colour and pod shape C. Seed shape and seed colour D. Flower position and seed shape

✅ Answer: C

📘 Explanation: Mendel selected seed shape (round/wrinkled) and seed colour (yellow/green).

3. Which of the following represents a pure-breeding round yellow pea plant?

A. RrYy B. RRyy C. rrYY D. RRYY

✅ Answer: D

📘 Explanation: Pure breeding dominant for both traits → RRYY.

4. The genotype of pure wrinkled green pea plant is

A. RrYy B. rrYY C. rryy D. RRYy

✅ Answer: C

📘 Explanation: Both traits recessive → rryy.

5. How many types of gametes are produced by RrYy genotype?

A. One B. Two C. Four D. Eight

✅ Answer: C

📘 Explanation: RrYy produces RY, Ry, rY, ry.

6. All F₁ plants of a dihybrid cross show

A. Recessive traits B. Variation C. Dominant traits D. Intermediate traits

✅ Answer: C

📘 Explanation: Dominant alleles express in F₁ generation.

7. The genotype of F₁ generation in Mendel’s dihybrid cross is

A. RRYY B. rryy C. RrYy D. RRYy

✅ Answer: C

📘 Explanation: Cross of RRYY × rryy gives RrYy.

8. Phenotypic ratio in F₂ generation of dihybrid cross is

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

✅ Answer: C

📘 Explanation: Four phenotypes appear in 9:3:3:1 ratio.

9. Which phenotype appears maximum times in F₂ generation?

A. Round green B. Wrinkled yellow C. Round yellow D. Wrinkled green

✅ Answer: C

📘 Explanation: Round yellow appears 9 out of 16 times.

10. Which phenotype appears least frequently in F₂ generation?

A. Round yellow B. Round green C. Wrinkled yellow D. Wrinkled green

✅ Answer: D

📘 Explanation: Wrinkled green (rryy) appears once.

11. Which Mendelian law is explained by dihybrid cross?

A. Law of dominance B. Law of segregation C. Law of independent assortment D. Law of purity of gametes

✅ Answer: C

📘 Explanation: Dihybrid cross demonstrates independent assortment.

12. Independent assortment means

A. Alleles blend together B. Alleles of one gene affect another C. Alleles of different genes assort independently D. Genes are linked

✅ Answer: C

📘 Explanation: Each gene pair segregates independently.

13. New trait combinations seen in F₂ generation are called

A. Parental types B. Dominant types C. Recombinant types D. Mutants

✅ Answer: C

📘 Explanation: New combinations formed due to independent assortment.

14. Which of the following is a recombinant phenotype?

A. Round yellow B. Wrinkled green C. Round green D. Both A and B

✅ Answer: C

📘 Explanation: Round green was not present in parents.

15. How many phenotypes appear in F₂ generation of dihybrid cross?

A. Two B. Three C. Four D. Sixteen

✅ Answer: C

📘 Explanation: Four phenotypes appear.

16. Total number of genotypic combinations in F₂ generation is

A. 4 B. 8 C. 9 D. 16

✅ Answer: D

📘 Explanation: 4 × 4 Punnett square = 16 combinations.

17. Which stage of meiosis is responsible for independent assortment?

A. Prophase I B. Metaphase I C. Anaphase II D. Telophase I

✅ Answer: B

📘 Explanation: Random alignment at Metaphase I causes assortment.

18. Independent assortment increases

A. Homozygosity B. Mutation C. Genetic variation D. Linkage

✅ Answer: C

📘 Explanation: It creates new allele combinations.

19. A dihybrid test cross is done with

A. Homozygous dominant B. Heterozygous C. Homozygous recessive D. F₁ plant

✅ Answer: C

📘 Explanation: Test cross uses double recessive parent (rryy).

20. Phenotypic ratio of a dihybrid test cross is

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

✅ Answer: D

📘 Explanation: Equal gametes give equal phenotypes.

21. Which genotype produces only one type of gamete?

A. RrYy B. RRYy C. RrYY D. RRYY

✅ Answer: D

📘 Explanation: RRYY produces only RY gamete.

22. Genes showing independent assortment are located on

A. Same locus B. Same chromosome C. Different chromosomes D. Centromere

✅ Answer: C

📘 Explanation: Different chromosomes assort independently.

23. Law of independent assortment fails in case of

A. Homozygous genes B. Dominant genes C. Linked genes D. Test cross

✅ Answer: C

📘 Explanation: Linked genes are inherited together.

24. The probability of getting wrinkled green seed in F₂ is

A. 1/4 B. 1/8 C. 1/16 D. 3/16

✅ Answer: C

📘 Explanation: rryy appears once in 16.

25. Which of the following is correct about F₁ generation?

A. Shows variation B. Shows recessive traits C. Is heterozygous for both genes D. Produces only one gamete

✅ Answer: C

📘 Explanation: All F₁ plants are RrYy.

26. Dihybrid phenotypic ratio is the product of

A. Mutation B. Two monohybrid ratios C. Crossing over D. Random fertilization

✅ Answer: B

📘 Explanation: (3:1) × (3:1) = 9:3:3:1.

27. Which scientist explained chromosomal basis of inheritance?

A. Mendel B. Darwin C. Sutton and Boveri D. Morgan

✅ Answer: C

📘 Explanation: They proposed the chromosomal theory of inheritance.

28. Which genotype gives round green seeds?

A. RRyy B. rrYY C. RrYy D. rryy

✅ Answer: A

📘 Explanation: Round (R) dominant + green (yy).

29. Which genotype gives wrinkled yellow seeds?

A. RRYy B. rrYY C. RrYy D. RRyy

✅ Answer: B

📘 Explanation: Wrinkled (rr) + yellow (Y).

30. Mendel’s dihybrid cross disproved

A. Evolution B. Mutation C. Blending inheritance D. Natural selection

✅ Answer: C

📘 Explanation: Traits do not blend; they remain discrete.

31. The phenotypic ratio 9 : 3 : 3 : 1 is obtained due to

A. Law of dominance B. Law of segregation C. Law of independent assortment D. Law of purity of gametes

✅ Correct Answer: C

📘 Explanation: The 9:3:3:1 phenotypic ratio appears only when two gene pairs assort independently during gamete formation. This is explained by Mendel’s Law of Independent Assortment, which states that alleles of different genes segregate independently during meiosis.

32. In a dihybrid cross, the number of different gametes produced by F₁ generation is

A. 1 B. 2 C. 3 D. 4

✅ Correct Answer: D

📘 Explanation: The F₁ generation has genotype RrYy. Gametes formed: RY, Ry, rY, ry Hence, 4 different gametes are produced.

33. Which of the following phenotypes represents a recombinant type?

A. Round yellow B. Wrinkled green C. Round green D. Round yellow and wrinkled green

✅ Correct Answer: C

📘 Explanation: Recombinant phenotypes are new combinations not present in parents. Parents: • Round yellow • Wrinkled green Recombinant: Round green and wrinkled yellow.

34. Independent assortment of genes occurs during

A. Prophase I B. Metaphase I C. Anaphase I D. Telophase II

✅ Correct Answer: B

📘 Explanation: During Metaphase I of meiosis, homologous chromosomes align randomly on the equatorial plate, leading to independent assortment of genes.

35. Which genotype produces only one type of gamete?

A. RrYy B. RRYy C. RrYY D. RRYY

✅ Correct Answer: D

📘 Explanation: The genotype RRYY is homozygous for both traits and produces only RY gamete.

36. The least frequent phenotype in F₂ generation of a dihybrid cross is

A. Round yellow B. Round green C. Wrinkled yellow D. Wrinkled green

✅ Correct Answer: D

📘 Explanation: Wrinkled green (rryy) appears only once out of 16, making it the least frequent phenotype.

37. The dihybrid phenotypic ratio is actually the product of

A. Mutation events B. Crossing over C. Two monohybrid ratios D. Chromosomal linkage

✅ Correct Answer: C

📘 Explanation: Each trait follows 3:1 ratio. So: (3:1) × (3:1) = 9:3:3:1

38. Which cross helps to determine the genotype of an organism?

A. Self cross B. Back cross C. Test cross D. Reciprocal cross

✅ Correct Answer: C

📘 Explanation: A test cross involves crossing an individual with a homozygous recessive to determine its genotype.

39. Phenotypic ratio of a dihybrid test cross is

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

✅ Correct Answer: D

📘 Explanation: In a dihybrid test cross: RrYy × rryy Four types of gametes are produced equally, giving 1:1:1:1 ratio.

40. Which statement best explains Mendel’s law of independent assortment?

A. Alleles blend together B. Traits are inherited together C. Alleles of one gene segregate independently of another D. Genes mutate frequently

✅ Correct Answer: C

📘 Explanation: Each gene pair behaves independently during gamete formation, provided the genes are not linked.

41. Independent assortment is possible only when genes are

A. Located on same locus B. Located on same chromosome C. Closely linked D. Located on different chromosomes

✅ Correct Answer: D

📘 Explanation: Genes located on different chromosomes assort independently during meiosis.

42. Which scientist experimentally proved chromosomal theory of inheritance?

A. Mendel B. Darwin C. Sutton and Boveri D. Watson and Crick

✅ Correct Answer: C

📘 Explanation: Sutton and Boveri correlated Mendel’s laws with chromosome behavior.

43. A cross between RrYy × rryy is an example of

A. Self cross B. Back cross C. Test cross D. Reciprocal cross

✅ Correct Answer: C

📘 Explanation: Crossing with double recessive (rryy) is always a test cross.

44. Which of the following increases genetic variation in offspring?

A. Mitosis B. Independent assortment C. Cloning D. Binary fission

✅ Correct Answer: B

📘 Explanation: Independent assortment creates new allele combinations, increasing variation.

45. The genotype rryy represents

A. Dominant phenotype B. Heterozygous condition C. Pure breeding recessive D. Recombinant genotype

✅ Correct Answer: C

📘 Explanation: rryy is homozygous recessive for both traits.

46. How many phenotypes appear in the F₂ generation of a dihybrid cross?

A. 2 B. 3 C. 4 D. 16

✅ Correct Answer: C

📘 Explanation: Four phenotypes: • Round yellow • Round green • Wrinkled yellow • Wrinkled green

47. Which law of Mendel fails in case of linked genes?

A. Law of dominance B. Law of segregation C. Law of independent assortment D. Law of inheritance ✅ Correct Answer: C 📘 Explanation: Linked genes are inherited together and do not assort independently.

48. The F₁ generation of a dihybrid cross is always

A. Homozygous B. Variable C. Uniform D. Recessive

✅ Correct Answer: C

📘 Explanation: All F₁ plants show uniform dominant phenotype.

49. Which genotype gives wrinkled yellow seeds?

A. RRYy B. rrYY C. RrYy D. RRyy

✅ Correct Answer: B

📘 Explanation: Wrinkled = rr (recessive) Yellow = Y (dominant)

50. Dihybrid cross laid the foundation for understanding

A. Mutation B. Linkage C. Polygenic inheritance D. Genetic variation

✅ Correct Answer: D

📘 Explanation: Dihybrid crosses explain how variation arises naturally in populations.

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Concepts: Inheritance of Two Genes (Dihybrid Inheritance)