| Distinguishing RNA Subsets |
In early cells that lacked DNA, a crucial problem was differentiating between two types of RNAs: messenger RNAs (mRNAs) that code for proteins, and heritable genetic RNAs that propagate genetic information through generations. |
| Role of Introns |
Scientists proposed that introns could serve as markers for these RNA subsets, directing them to different functions. This helped in the early differentiation and proper functioning of various RNA molecules. |
| Ancient Feature of Genome |
The split-gene arrangement, which includes both introns and exons, is an ancient feature of the genome. This structure was present even when RNA was the primary genetic material, indicating its long evolutionary history. |
| Introns and Antiquity |
The presence of introns is reminiscent of ancient times, when they were crucial for distinguishing mRNA from genomic RNA. Although introns are largely non-functional today, their existence points to their historical significance in early RNA processing. |
| RNA Splicing and Dominance |
Splicing is the process of removing introns from the primary RNA transcript, catalyzed by small nuclear RNAs (snRNAs like U1, U2, U4, U5, and U6). This process reflects the dominance of the RNA world, when RNA-based mechanisms were essential for genetic processing and regulation before the emergence of DNA. |
| RNA vs. DNA Dominance |
RNA splicing highlights the dominance of RNA because RNA can remove introns and retain exons, whereas DNA retains introns. This indicates how RNA was and remains a dominant molecule in genetic processes, showcasing its evolutionary precedence over DNA. |
