Q.13 Determine the correctness or otherwise of the following Assertion [a] and the
Reason [r].
Assertion [a]: In multicellular organisms, cells of different lineages have different
gene expression profiles.
Reason [r]: Alternative splicing is the only mechanism to generate protein
diversity.
(A) Both [a] and [r] are false
(B) Both [a] and [r] are true and [r] is the correct reason for [a]
(C) Both [a] and [r] are true but [r] is not the correct reason for [a]
(D) [a] is true but [r] is false

Correct answer: (D) [a] is true but [r] is false.

Assertion [a] holds true because multicellular organisms differentiate cells into lineages like neurons or muscle cells through distinct gene expression profiles, where specific genes activate or repress based on developmental signals and transcription factors.​

Reason [r] is false since alternative splicing, while key for creating mRNA isoforms from one gene, is not the sole mechanism for protein diversity; others include post-translational modifications, gene duplication, allelic variations, and RNA editing.​

Option (A) fails as [a] is true. Option (B) fails because [r] is false and unrelated to [a]. Option (C) fails due to [r]’s falsity. Thus, (D) fits perfectly.​

In multicellular organisms, cells of different lineages exhibit unique gene expression profiles, enabling specialization from stem cells to tissues like liver or brain. This query from GATE BT 2023 tests understanding of cell differentiation versus mechanisms like alternative splicing for protein diversity.​

Assertion [a] Analysis

Cells in lineages such as ectoderm or mesoderm show varied gene expression via epigenetic controls and transcription factors, producing lineage-specific proteomes despite shared genomes.​

Reason [r] Evaluation

Alternative splicing generates protein isoforms by exon shuffling, common in eukaryotes, but ignores other paths like proteolytic cleavage or phosphorylation that expand proteome complexity.​

Option Breakdown

• (A) Both false: Incorrect; [a] reflects differentiation reality.​

• (B) Both true, [r] explains [a]: Wrong; [r] false and unrelated to expression profiles.

• (C) Both true, unrelated: Invalid as [r] false.

• (D) [a] true, [r] false: Correct; matches biology facts.​