Question

What was the "RNA World"? What evidence is there that RNA was an important component of the common ancestor of all present (existing) forms of life (on earth)?

Answer 1

The RNA world is a hypothetical entity which states that RNA remains the major molecule for evolution of life on earth, not DNA. There are some unique properties of the RNA which makes it a suitable candidate for being considered as the molecule associated with evolution. These properties can be discussed as below:

1. RNA is self-replicating and can exist in stable form even under single-stranded forms.
2. RNA is self-splicing in nature and does not require any other enzymes for its architectural remodelling.
3. RNA represents the store-house of genetic information as well.
4. RNA can catalyze the rate of reactions, such as ribozymes.
5. RNA also functions as a co-factor of many complex bio-molecules ribosomal complex, and hence serves as self-stabilizing.
6. RNA alone can serve as the genetic material in a cell even in the absence of DNA.

Thus, this states that the RNA world entity has many positive arguments to consider RNA as the evolutionary molecule.

The presence of RNA as a genetic material in many viruses and the primitive associationship between the RNA sequences/molecules of prokaryotes and eukaryotes further emphasizes on the possibility of this hypothesis.