Final answer:
The RNA world hypothesis presents the idea that RNA was the first complex molecule, central to the origin of life, eventually giving rise to DNA and proteins. It includes chemical evolution by primitive molecules, RNA formation, self-replication, RNA-based life, and the transition to the current DNA/RNA/protein world.
Step-by-step explanation:
The RNA world hypothesis is a well-supported theory regarding the origin of life on Earth. This hypothesis can be summarized in five key steps:
- Chemical Evolution: Before life existed, simple organic molecules formed under prebiotic conditions, as demonstrated by the Miller-Urey experiment.
- RNA Formation: Among these organic molecules, RNA emerged as a versatile molecule capable of storing genetic information and catalyzing chemical reactions.
- Self-Replication: As a single-stranded molecule, RNA had the ability to fold in various ways, catalyze its own replication, and evolve through natural selection.
- RNA-Based Life: Before the evolution of DNA and proteins, primitive organisms based solely on RNA could have existed, performing all necessary cellular functions.
- Transition to DNA/RNA/Protein World: Eventually, RNA organisms developed the ability to use DNA as a more stable repository of genetic information and proteins to carry out catalysis more efficiently, leading to the transition towards the DNA/RNA/protein world we see today.
The RNA world hypothesis is supported by the fact that ribosomal RNA (rRNA) catalyzes peptide bond formation during protein synthesis, suggesting a historical precedent where RNA played both the informational and catalytic roles.