Question

Arrange the following steps involved in the regulation of gene expression in correct sequence.
(A) Processing level
(B) Translational level
(C) Transcriptional level
(D) Transport of mRNA from the nucleus to the cytoplasm
Choose the correct answer from the options given below:

• A. (B), (A), (D), (C)
• B. (D), (B), (A), (C)
• C. (C), (A), (D), (B)
• D. (A), (D), (B), (C)

Hint:

Flow of Eukaryotic Gene Regulation:
1. Transcription (hnRNA synthesis)
2. Processing (Splicing, Capping, Tailing)
3. Nuclear Transport (Nucleus to Cytoplasm)
4. Translation (Polypeptide synthesis)

Answer 1

The Correct Option is C

Concept:
In eukaryotic organisms, gene expression is a multi-step process leading to the synthesis of a functional protein. Regulation can occur at several sequential stages along this biological pathway.

Step 1: Sequential Levels of Gene Regulation in Eukaryotes:
In eukaryotes, gene expression is regulated in the following chronological sequence from the gene in the nucleus to the finished protein in the cytoplasm:
1. Transcriptional level (C): Formation of the primary RNA transcript (hnRNA) from the DNA template in the nucleus.
2. Processing level (A): Post-transcriptional modification of primary transcripts, including 5'-capping, 3'-polyadenylation, and splicing of non-coding introns to form mature mRNA.
3. Transport level (D): Transport of the processed, mature mRNA through nuclear pore complexes from the nucleus into the cytoplasm.
4. Translational level (B): Translation of mRNA into a polypeptide chain by ribosomes and tRNAs in the cytoplasm.

Step 2: Compiling the Sequence:
The chronological order of gene regulation steps is:
Transcriptional level (C) $\rightarrow$ Processing level (A) $\rightarrow$ Transport of mRNA (D) $\rightarrow$ Translational level (B).
This matches sequence (C), (A), (D), (B).

Step 3: Final Answer:
Thus, the correct option is (C).