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Home Questions 7X8MTKXHVY
Target Exam

CUET

Subject

Biology

Chapter

Principles of Inheritance and Variation

Question:

Match List-I with List-II

List-I List-II
Types of inheritance Examples
(A). Pleiotropy (I). ABO blood grouping in human
(B). Polygenic inheritance (II). Snapdragon plant
(C). Incomplete dominance (III). Phenylketonuria
(D). Co-dominance (IV). Human skin colour

Choose the correct answer from the options given below:

Options:

(A)-(III), (B) -(IV), (C) - (II), (D) - (I)

(A)-(I), (B) -(III), (C) - (II), (D) - (IV)

(A)-(I), (B) -(II), (C) - (IV), (D) - (III)

(A)-(III), (B) -(IV), (C) - (I), (D) - (II)

Correct Answer:

(A)-(III), (B) -(IV), (C) - (II), (D) - (I)

Explanation:

The correct answer is Option (1) → (A)-(III), (B) -(IV), (C) - (II), (D) - (I)

List-I List-II
Types of inheritance Examples
(A). Pleiotropy (III). Phenylketonuria
(B). Polygenic inheritance (IV). Human skin colour
(C). Incomplete dominance (II). Snapdragon plant
(D). Co-dominance (I). ABO blood grouping in human

A. When a single gene can exhibit multiple phenotypic expression such a gene is called a pleiotropic gene. The underlying mechanism of pleiotropy in most cases is the effect of a gene on metabolic pathways which contribute towards different phenotypes. An example of this is the disease phenylketonuria, which occurs in humans. The disease is caused by mutation in the gene that codes for the enzyme phenyl alanine hydroxylase (single gene mutation). This manifests itself through phenotypic expression characterised by mental retardation and a reduction in hair and skin pigmentation.

B. Polygenic inheritance involves the influence of multiple genes on a single phenotypic trait. Polygenic inheritance is an inheritance pattern controlled by three or more genes (multiple genes) and the graded phenotypes are due to the additive or cumulative effect of all the different genes of the trait. An example of human skin colour to understand the phenomenon of polygenic inheritance.

C. The inheritance of flower colour in the dog flower (snapdragon or Antirrhinum sp.) is a good example to understand incomplete dominance. In a cross between true-breeding red-flowered (RR) and true- breeding white-flowered plants (rr), the F1 (Rr) was pink. When the F1 was self-pollinated the F2 resulted in the following ratio 1 (RR) Red : 2 (Rr) Pink : 1 (rr) White. 

D. Co-dominance occurs when both alleles in a heterozygous individual contribute to the phenotype. In the case of the ABO blood group system, the IA and IB alleles are co-dominant. This means that if an individual has both IA and IB alleles (genotype IAIB), both alleles are expressed, and the individual has blood type AB, which has both A and B antigens on the surface of the red blood cells. A good example of co-dominance is different types of red blood cells that determine ABO blood grouping in human beings.

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