In the ABO blood group system, the 'I' gene has three alleles: IA, IB, and i. When a person has the genotype IAIB, they express both A and B antigens. This is an example of: MCQ with Answer and Explanation

Question

In the ABO blood group system, the 'I' gene has three alleles: IA, IB, and i. When a person has the genotype IAIB, they express both A and B antigens. This is an example of:

A. Codominance

B. Multiple allelism only

C. Pleiotropy

D. Incomplete dominance

Answer: Option A

Solution (By JKExamLibrary)

Codominance occurs when two different alleles of a gene are fully and equally expressed in the heterozygous condition. In the ABO blood group, the IA and IB alleles are codominant. An individual with the genotype IAIB produces both A and B antigens on the surface of their red blood cells, resulting in the AB blood type. While the ABO system also involves multiple alleles (IA, IB, i), the specific expression of both antigens is codominance.

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The structural polysaccharide that forms the exoskeleton of arthropods is:

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Correct Answer: Option B

Explanation:
Chitin is a polymer of N-acetylglucosamine, forming the tough exoskeleton of arthropods and the cell wall of fungi. Cellulose is a plant polysaccharide, starch and glycogen are energy storage polysaccharides in plants and animals respectively. Chitin provides protection and support.

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Consider the following statements about cell theory:
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Correct Answer: Option A

Explanation:
The modern cell theory includes all three statements: (1) all organisms are made of cells, (2) the cell is the basic unit of life, and (3) cells arise from pre-existing cells (Omnis cellula e cellula). Thus, all three are correct. This theory was formulated by Schleiden, Schwann, and Virchow.

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Correct Answer: Option B

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