The split-gene arrangement probably represents an ancient feature of the genome. The presence of introns is reminiscent of ...A..., and the process of splicing represents the dominance of ...B....
Here A and B refer to:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A–antiquity, B–RNA-world
In eukaryotes, genes are split: the coding sequences (exons) are interrupted by non-coding sequences (introns). After transcription, the introns are cut out and the exons are joined; this is splicing. The book treats this split arrangement as a very old feature of the genome.
Blank A – antiquity. Introns point back to the ancient past (antiquity) of the genome. “Recent evolution” is the opposite idea, so it cannot fill blank A.
Blank B – RNA-world. Splicing is a process carried out on RNA, and the book says it represents the dominance of the RNA-world, the early stage of life when RNA was the main genetic and catalytic molecule. A “DNA-world” or “protein-world” does not match a process that works on RNA.
NCERT Extract:
Types of RNA and the Process of Transcription – “… The significance of such complexities is now beginning to be understood. The split-gene arrangements represent probably an ancient feature of the genome. The presence of introns is reminiscent of antiquity, and the process of splicing represents the dominance of RNA-world. In recent times, the understanding of RNA and RNA-dependent processes in the living system have assumed more importance.”