Free Inheritance MCQs with Answers

51. Incomplete dominance results in

• A. Only dominant phenotype
• B. Only recessive phenotype
• C. Intermediate phenotype
• D. Both phenotypes expressed

Explanation: In incomplete dominance, the heterozygote shows an intermediate phenotype, e.g., pink flowers from red and white parents.

52. ABO blood group inheritance demonstrates

• A. Complete dominance only
• B. Incomplete dominance
• C. Codominance and multiple alleles
• D. Sex linkage

Explanation: ABO system shows codominance (IA and IB both expressed in AB) and multiple alleles (IA, IB, i).

53. Haemophilia is

• A. Autosomal dominant
• B. Autosomal recessive
• C. X-linked recessive
• D. Y-linked

Explanation: Haemophilia is an X-linked recessive disorder affecting blood clotting, more common in males.

54. Linkage between genes

• A. Increases with distance on chromosome
• B. Decreases with distance
• C. Is unaffected by distance
• D. Only occurs on sex chromosomes

Explanation: Linkage decreases with distance; genes farther apart cross over more frequently. 1% recombination = 1 map unit.

55. In Hardy-Weinberg equilibrium, p² represents

• A. Heterozygote frequency
• B. Homozygous dominant frequency
• C. Homozygous recessive frequency
• D. Total alleles

Explanation: p² = frequency of homozygous dominant (AA), 2pq = heterozygous (Aa), q² = homozygous recessive (aa).

56. Polygenic inheritance involves

• A. One gene with two alleles
• B. Multiple genes affecting one trait
• C. Genes on sex chromosomes only
• D. Mitochondrial genes

Explanation: Polygenic traits (height, skin color) are controlled by multiple genes, showing continuous variation.

57. A carrier of an X-linked recessive disorder is

• A. Male with the disorder
• B. Female with one affected X
• C. Female with both X affected
• D. Male without the disorder

Explanation: Carrier females are heterozygous (XAXa) and phenotypically normal but can pass the allele to offspring.

58. Pleiotropy refers to

• A. One gene affecting multiple traits
• B. Multiple genes affecting one trait
• C. Genes on same chromosome
• D. Genes affecting only one tissue

Explanation: Pleiotropy is when one gene affects multiple phenotypic traits, e.g., sickle cell gene affects multiple organs.

59. The 9:3:3:1 ratio of law of independent assortment can be affected by

• A. Genetic drift
• B. Small population
• C. Gene linkage
• D. Gene duplication

Explanation: Independent assortment requires the two genes to be on different chromosomes, so genes linked on the same chromosome travel together and the dihybrid ratio departs from 9:3:3:1, with parental combinations over represented. Genetic drift and small population size shift allele frequencies across generations rather than distorting the ratio within a single cross. Crossing over partly restores the expected ratio by separating linked genes.

60. Best description of the process of crossing over during meiosis:

• A. Duplication of chromosome
• B. Exchange of genes between non-sister chromatids
• C. Movement of chromosome to opposite poles
• D. Separation of sister chromatids

Explanation: During prophase I the homologues pair as bivalents and non sister chromatids exchange equal segments at chiasmata, producing chromosomes carrying combinations neither parent had. The exchange must be between non sister chromatids, since sister chromatids are identical and swapping between them would change nothing. Separation of sister chromatids happens later, in anaphase II.