NEET 2025 MCQ with Answer Explanation : “Inheritance Chapter”.

Here below some MCQ with answer of inheritance chapter. Which is explained in details. Let’s check one by one.

1. Which of the following is an example of incomplete dominance?
   a) Blood group inheritance in humans
   b) Flower color in Mirabilis jalapa
   c) Skin color in humans
   d) Eye color inheritance in humans

Answer: (b) Flower color in Mirabilis jalapa

Explanation: In incomplete dominance, the heterozygous offspring shows a phenotype that is an intermediate of the two homozygous parents. In Mirabilis jalapa (Four O’clock plant), when a red-flowered plant (RR) is crossed with a white-flowered plant (rr), the offspring (Rr) have pink flowers. Neither the red nor the white allele is completely dominant over the other.

2. Which of the following conditions is not a part of Mendel’s law of segregation?
   a) Each individual possesses two alleles for each trait
   b) Alleles segregate during gamete formation
   c) Alleles blend together in the offspring
   d) Gametes receive only one allele for each trait

Answer: (c) Alleles blend together in the offspring

Explanation: According to Mendel’s law of segregation, alleles separate or segregate during gamete formation, and each gamete receives only one allele for each trait. This law contradicts the blending inheritance theory, where it was once believed that traits blend in offspring. Mendel showed that alleles remain distinct and do not blend.

3. What is the phenotypic ratio in a dihybrid cross when both traits exhibit complete dominance?
   a) 9:3:3:1
   b) 1:2:1
   c) 3:1
   d) 1:1:1:1

Answer: (a) 9:3:3:1

Explanation: In a dihybrid cross (crossing two individuals that are heterozygous for two traits), the phenotypic ratio observed is 9:3:3:1. This occurs when both traits exhibit complete dominance. For example, in a cross between two pea plants heterozygous for seed color (yellow dominant over green) and seed shape (round dominant over wrinkled), the ratio of phenotypes in the offspring would be 9 yellow round: 3 yellow wrinkled: 3 green round: 1 green wrinkled.

4. A man with blood group A marries a woman with blood group B. They have a child with blood group O. What are the possible genotypes of the parents?
   a) IAIA and IBIB
   b) IAi and IBi
   c) IAIA and IBi
   d) IAi and IBIB

Answer: (b) IAi and IBi

Explanation: Blood group O is only possible if both parents carry the recessive “i” allele. Therefore, the parents must have the genotypes IAi (father) and IBi (mother). This combination allows for the possibility of their child inheriting the “i” allele from both parents, resulting in blood group O.

5. Which of the following disorders is an example of sex-linked inheritance?
   a) Down syndrome
   b) Sickle cell anemia
   c) Hemophilia
   d) Cystic fibrosis

Answer: (c) Hemophilia

Explanation: Hemophilia is a sex-linked recessive disorder, meaning it is carried on the X chromosome. Since males have only one X chromosome (XY), they are more likely to express the disorder if they inherit the affected X chromosome. Females (XX) are usually carriers unless they inherit the mutated gene on both X chromosomes. The other conditions mentioned are autosomal disorders.

6. What is the cause of variation in offspring according to Mendel’s principles?
   a) Random fusion of gametes
   b) Mutations
   c) Law of independent assortment
   d) Environmental factors

Answer: (c) Law of independent assortment

Explanation: Mendel’s law of independent assortment states that genes for different traits assort independently of one another during gamete formation. This means that the allele a gamete receives for one trait does not affect the allele received for another trait, leading to variation in the offspring. Although random fusion of gametes and mutations also contribute to genetic variation, Mendel’s principle specifically refers to independent assortment as the cause of variation.

7. Which of the following statements is true regarding a test cross?
   a) It is performed to determine the genotype of a dominant individual.
   b) It is a cross between two heterozygous individuals.
   c) It is performed to determine the phenotype of an organism.
   d) It is performed between two recessive individuals.

Answer: (a) It is performed to determine the genotype of a dominant individual.

Explanation: A test cross is a cross between an individual showing a dominant phenotype (but with an unknown genotype) and a homozygous recessive individual. It helps determine whether the dominant individual is homozygous (pure) or heterozygous for that trait. If any offspring show the recessive trait, the dominant individual must be heterozygous.

8. In a test cross involving F1 dihybrid flies, more parental-type offspring were produced than recombinant-type offspring. This indicates that the genes are:
   a) On different chromosomes
   b) Linked and far apart
   c) Linked and close together
   d) Unlinked and assort independently

Answer: (c) Linked and close together

Explanation: When genes are located close together on the same chromosome, they tend to be inherited together, which results in more parental-type offspring than recombinant-type. This phenomenon is known as gene linkage. If genes were far apart or on different chromosomes, there would be more recombination, leading to a higher frequency of recombinant offspring.

9. The phenomenon where a single gene influences multiple traits is called:
   a) Codominance
   b) Epistasis
   c) Pleiotropy
   d) Polygenic inheritance

Answer: (c) Pleiotropy

Explanation: Pleiotropy occurs when a single gene affects multiple phenotypic traits. For example, the gene responsible for sickle-cell anemia affects the shape of red blood cells, as well as the oxygen-carrying capacity, resistance to malaria, and can cause various health complications. In contrast, polygenic inheritance involves multiple genes affecting a single trait.

10. Which of the following traits in humans is an example of polygenic inheritance?
    a) Blood group
    b) Height
    c) Earlobe shape
    d) Tongue rolling ability

Answer: (b) Height

Explanation: Polygenic inheritance occurs when multiple genes influence a single trait. Height in humans is controlled by the interaction of several genes, making it a polygenic trait. Traits like blood group and tongue rolling ability are examples of single-gene traits, while earlobe shape may have a more complex inheritance but is not an example of polygenic inheritance.