According to the RNA World Hypothesis, which molecule is thought to have arisen first?

The RNA World Hypothesis posits that RNA was one of the first molecules that were capable of self-replication and catalyzing biochemical reactions, predating both DNA and proteins in the evolution of life. This hypothesis is supported by several key characteristics of RNA.

First, RNA possesses the ability to store genetic information like DNA while also having catalytic properties akin to proteins. Ribozymes, which are RNA molecules that can catalyze chemical reactions, illustrate RNA's potential to facilitate biochemical processes without the need for protein enzymes. This dual functionality suggests that early life forms could have relied solely on RNA for both genetic replication and metabolic functions.

Furthermore, the transition from RNA to DNA-based life is thought to have occurred later, as DNA is more stable and less prone to mutation over time compared to RNA. This stability would offer a more reliable means of storing genetic information as life evolved.

The other options, such as proteins, disease-causing viruses, and DNA, represent more complex biochemical entities that are considered to have developed after the initial RNA-based life forms. Thus, RNA is viewed as the foundational molecule in the evolutionary timeline leading to modern cellular life.