Observe the given figure and answer the question.

Identify the correct sequence of events occurring in the process shown in the figure.

(A) Tailing and Splicing

(B) Transport of the molecule out of the nucleus

(C) Transcription of precursor RNA by RNA polymerase II

(D) Capping

Choose the correct answer from the options given below:

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

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

Transcription of precursor RNA by RNA polymerase II (C): The process of gene expression starts with the transcription of the DNA sequence into a precursor RNA molecule by RNA polymerase II. This RNA molecule contains both exons (coding regions) and introns (non-coding regions).

Capping (D): ) Primary transcripts contain both the exons and the introns and are non-functional. Hence, it is subjected to a process called splicing where the introns are removed and exons are joined in a defined order. hnRNA undergoes additional processing called as capping and tailing. In capping an unusual nucleotide (methyl guanosine triphosphate) is added to the 5'-end of hnRNA.

Tailing and Splicing (A): In tailing, adenylate residues (200-300) are added at 3'-end in a template independent manner. It is the fully processed hnRNA, now called mRNA.

Transport of the molecule out of the nucleus (B): Once the mRNA molecule is fully processed, including capping, tailing, and splicing, it is ready to be transported out of the nucleus into the cytoplasm. In the cytoplasm, the mature mRNA can undergo translation to produce proteins.