Arrange the given steps for regulation of gene expression in correct sequence?

(A) Regulation of splicing
(B) Transport of mRNA from the nucleus to the cytoplasm
(C) Translation
(D) Formation of primary transcript (Transcription)

Choose the correct answer from the options given below:

(D), (A), (B), (C)

The correct answer is Option (3) → (D), (A), (B), (C) 

Explanation of the Sequence

Gene expression is the process by which the information encoded in a gene is used to synthesize a functional gene product, usually a protein. The regulation of this process can occur at multiple levels in eukaryotes. The correct order of these steps is:

(D) Formation of primary transcript (Transcription): This is the first step where the DNA sequence of a gene is copied into a pre-mRNA molecule, also known as the primary transcript. This process occurs in the nucleus. Regulation at this stage, known as transcriptional regulation, determines which genes are transcribed and at what rate.

(A) Regulation of splicing: After transcription, the pre-mRNA molecule undergoes processing. This includes the removal of non-coding introns and the joining of coding exons in a process called splicing. The regulation of this step, known as post-transcriptional regulation, can create different protein isoforms from a single gene.

(B) Transport of mRNA from the nucleus to the cytoplasm: Once processed, the mature mRNA molecule must be exported from the nucleus to the cytoplasm, where protein synthesis occurs. The cell can regulate the amount of mRNA that reaches the cytoplasm, thus controlling gene expression.

(C) Translation: In the cytoplasm, the mRNA molecule is used as a template to synthesize a protein by ribosomes. This process is called translation. The cell can regulate the rate of translation and the stability of the mRNA molecule, both of which affect the final amount of protein produced.

This sequence represents the flow of genetic information from DNA to a functional protein, with regulatory checkpoints at each stage.