Principles of Inheritance – Daily Practice Problem (DPP)

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🎯 NEET 2026 Daily Practice Problem (DPP)

Class 12 | Unit 2: Genetics | Topic: Principles of Inheritance

Q1. How many true-breeding pea plant varieties did Mendel select as pairs which were similar except for one character with contrasting traits?

  1. 7
  2. 14
  3. 21
  4. 4
✅ View Answer & Explanation

Correct Answer: (2) 14
Explanation: Mendel selected 14 true-breeding pea plant varieties (7 pairs of contrasting traits like tall/dwarf, violet/white flower, etc.).

Q2. A Test Cross is used to determine:

  1. The genotype of a plant with a dominant phenotype
  2. The phenotype of a plant with a recessive genotype
  3. Whether two species will breed successfully
  4. The number of alleles in a gene
✅ View Answer & Explanation

Correct Answer: (1) The genotype of a plant with a dominant phenotype
Explanation: By crossing a dominant phenotype (unknown genotype, e.g., Tt or TT) with a recessive parent (tt), the resulting ratio (1:1 or all dominant) reveals the unknown genotype.

[Image of a diagrammatic representation of a monohybrid cross]

Q3. ABO blood grouping in humans provides an example of:

  1. Incomplete dominance
  2. Co-dominance
  3. Multiple allelism
  4. Both 2 and 3
✅ View Answer & Explanation

Correct Answer: (4) Both 2 and 3
Explanation: It shows Co-dominance (alleles $I^A$ and $I^B$ express together in blood group AB) and Multiple Allelism (three alleles $I^A, I^B, i$ govern the character).

Q4. In Snapdragon (Antirrhinum sp.), a cross between a red flower (RR) and a white flower (rr) results in pink flowers (Rr). This is due to:

  1. Co-dominance
  2. Incomplete dominance
  3. Epistasis
  4. Pleiotropy
✅ View Answer & Explanation

Correct Answer: (2) Incomplete dominance
Explanation: The dominant allele is not fully dominant over the recessive allele, resulting in an intermediate phenotype (Pink).

Q5. The Chromosomal Theory of Inheritance was proposed by:

  1. Watson and Crick
  2. Sutton and Boveri
  3. Morgan and Sturtevant
  4. Mendel
✅ View Answer & Explanation

Correct Answer: (2) Sutton and Boveri
Explanation: Walter Sutton and Theodore Boveri noted that the behavior of chromosomes was parallel to the behavior of genes and used chromosome movement to explain Mendel’s laws.

Q6. Experimental verification of the chromosomal theory of inheritance was done by:

  1. Thomas Hunt Morgan
  2. Gregor Mendel
  3. Sutton
  4. Henking
✅ View Answer & Explanation

Correct Answer: (1) Thomas Hunt Morgan
Explanation: T.H. Morgan worked with fruit flies (Drosophila melanogaster) and discovered linkage and sex-linkage.

Q7. In birds, sex determination is of which type?

  1. XX – XY
  2. XX – XO
  3. ZZ – ZW
  4. ZO – ZZ
✅ View Answer & Explanation

Correct Answer: (3) ZZ – ZW
Explanation: In birds, females are heterogametic (ZW) producing two types of eggs, and males are homogametic (ZZ).

Q8. Sickle-cell anaemia is caused by the substitution of Glutamic acid by Valine at which position of the beta-globin chain?

  1. 4th position
  2. 6th position
  3. 10th position
  4. 12th position
✅ View Answer & Explanation

Correct Answer: (2) 6th position
Explanation: It is a point mutation where GAG (Glutamic acid) is replaced by GUG (Valine) at the 6th position of the beta-globin chain of haemoglobin.

Q9. Down’s syndrome is due to:

  1. Monosomy of 21st chromosome
  2. Trisomy of 21st chromosome
  3. Nullisomy of 21st chromosome
  4. Trisomy of 18th chromosome
✅ View Answer & Explanation

Correct Answer: (2) Trisomy of 21st chromosome
Explanation: It is caused by the presence of an additional copy of chromosome number 21 (47, XX, +21 or 47, XY, +21). First described by Langdon Down.

Q10. Haemophilia is a:

  1. Y-linked disorder
  2. Autosomal dominant disorder
  3. X-linked recessive disorder
  4. Autosomal recessive disorder
✅ View Answer & Explanation

Correct Answer: (3) X-linked recessive disorder
Explanation: It shows criss-cross inheritance (carrier mother to son). Females are rarely haemophilic because the mother must be a carrier and the father haemophilic.

Q11. The karyotype of an individual with Turner’s syndrome is:

  1. 47, XXY
  2. 45, XO
  3. 47, XXX
  4. 45, YO
✅ View Answer & Explanation

Correct Answer: (2) 45, XO
Explanation: Turner’s syndrome is caused by the absence of one of the X chromosomes in females. Such females are sterile with rudimentary ovaries.

Q12. Klinefelter’s Syndrome is characterized by:

  1. Short stature and furrowed tongue
  2. Gynecomastia and sterility
  3. Mental retardation only
  4. Absence of secondary sexual characters
✅ View Answer & Explanation

Correct Answer: (2) Gynecomastia and sterility
Explanation: Karyotype 47, XXY. Individuals are males with overall masculine development but show feminine development (breast development/gynecomastia) and are sterile.

Q13. Phenylketonuria is an inborn error of metabolism caused by the lack of enzyme:

  1. Tyrosinase
  2. Phenylalanine hydroxylase
  3. Homogentisic acid oxidase
  4. Hexosaminidase
✅ View Answer & Explanation

Correct Answer: (2) Phenylalanine hydroxylase
Explanation: This enzyme converts phenylalanine to tyrosine. Its absence leads to accumulation of phenylalanine, causing mental retardation.

Q14. The term ‘Linkage’ was coined by:

  1. Mendel
  2. Bateson
  3. Morgan
  4. Punnett
✅ View Answer & Explanation

Correct Answer: (3) Morgan
Explanation: Morgan coined ‘Linkage’ to describe the physical association of genes on a chromosome and ‘Recombination’ for the generation of non-parental gene combinations.

Q15. Human skin colour is an example of:

  1. Co-dominance
  2. Polygenic inheritance
  3. Pleiotropy
  4. Multiple alleles
✅ View Answer & Explanation

Correct Answer: (2) Polygenic inheritance
Explanation: Traits controlled by three or more genes (e.g., A, B, C) are called polygenic traits. They show a continuous variation.

Q16. Pleiotropy refers to:

  1. Multiple genes controlling one character
  2. One gene controlling multiple phenotypic expressions
  3. Genes located on the same chromosome
  4. Alleles that are co-dominant
✅ View Answer & Explanation

Correct Answer: (2) One gene controlling multiple phenotypic expressions
Explanation: A single gene can exhibit multiple phenotypic expressions. Example: The gene causing Phenylketonuria affects mental retardation, hair pigmentation, and skin color.

Q17. Which genetic disorder in humans is caused by an autosome linked recessive trait?

  1. Haemophilia
  2. Colour blindness
  3. Sickle-cell anaemia
  4. Hypertrichosis
✅ View Answer & Explanation

Correct Answer: (3) Sickle-cell anaemia
Explanation: Sickle-cell anaemia, Phenylketonuria, and Thalassemia are autosomal recessive disorders. Haemophilia and Colour blindness are X-linked recessive.

Q18. Sex determination in honey bees is based on:

  1. Temperature
  2. Chromosomal ratio (X/A ratio)
  3. Haplodiploidy
  4. XX-XO method
✅ View Answer & Explanation

Correct Answer: (3) Haplodiploidy
Explanation: Females are diploid (32 chromosomes) formed by fertilization, while males (drones) are haploid (16 chromosomes) formed by parthenogenesis.

Q19. The phenotypic ratio of a Mendelian Dihybrid cross is:

  1. 1:2:1
  2. 3:1
  3. 9:3:3:1
  4. 9:7
✅ View Answer & Explanation

Correct Answer: (3) 9:3:3:1
Explanation: In the F2 generation of a dihybrid cross (e.g., Round Yellow x Wrinkled Green), the phenotypic ratio is 9:3:3:1.

Q20. Failure of segregation of chromatids during cell division cycle results in the gain or loss of a chromosome(s), called:

  1. Polyploidy
  2. Aneuploidy
  3. Point mutation
  4. Frameshift mutation
✅ View Answer & Explanation

Correct Answer: (2) Aneuploidy
Explanation: Aneuploidy is the gain or loss of one or few chromosomes (e.g., 2n+1, 2n-1). Polyploidy is the increase in a whole set of chromosomes (e.g., 3n, 4n).

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