Question

Reflect and Apply RNA is often characterized as being the first "biologically active" molecule. What two properties or activities does RNA display that are important to the evolution of life? Hint: Neither proteins nor DNA have both of these properties.

Short answer

RNA stores genetic information and acts as a catalyst in biochemical reactions.

Step-by-step solution

- Understand the Importance of RNA

Begin by understanding why RNA is considered the first 'biologically active' molecule. RNA has unique characteristics that neither proteins nor DNA possess simultaneously.

- Identify RNA's Role in Genetic Information

RNA can store genetic information like DNA. This is crucial for the evolution of life as it allows RNA to carry the instructions for the synthesis of proteins.

- RNA's Catalytic Activity

RNA can also act as a catalyst in biochemical reactions. This allows it to facilitate chemical reactions, a role mainly played by proteins in cells.

Key concepts

RNA genetic storage

RNA plays a significant role in the storage of genetic information, much like DNA. This capability is crucial for the evolution of life because it allows RNA to carry the instructions required for building and maintaining an organism. By storing genetic codes, RNA can guide the synthesis of proteins which are essential for various life processes.
RNA is composed of nucleotides, similar to DNA, but it is typically single-stranded. The genetic information in RNA is encoded in sequences of four types of nucleotides, represented by the bases adenine (A), uracil (U), cytosine (C), and guanine (G). These sequences allow RNA to store and transmit genetic information efficiently.
In the context of early life forms, RNA's ability to store genetic information would have been vital for replication and passing on traits to subsequent generations. This unique feature sets RNA apart from proteins, which cannot store genetic information, and DNA, which cannot catalyze reactions.

RNA catalytic activity

One of the most fascinating properties of RNA is its catalytic ability, allowing it to facilitate biochemical reactions. Molecules capable of this are known as ribozymes. Unlike proteins, which require other proteins (enzymes) to catalyze reactions, RNA can act independently.
This catalytic activity is significant because it supports the 'RNA world' hypothesis. This hypothesis suggests that early life forms relied solely on RNA for both genetic storage and chemical reactions. For example, RNA molecules can catalyze the formation of peptide bonds, linking amino acids to form proteins. They can also catalyze their own synthesis and replication, an essential feature for the self-sustenance and propagation of early life.
Given that no such role is played by DNA, RNA's dual functionality has profound implications for our understanding of the origin and evolution of life.

evolution of life

The evolution of life on earth is intricately tied to the properties of RNA. The 'RNA world' hypothesis posits that early life was based solely on RNA, acting both as a genetic material and as a catalyst for biochemical reactions. This dual role would have offered a simpler and more efficient mechanism for life to flourish in primordial conditions.
Over time, as life forms evolved, the more stable DNA took over the role of genetic storage, while proteins, which are more versatile catalysts, took over the enzymatic activities. However, the early role of RNA remains critical in understanding the fundamental processes that led to the complexity of life as we know it today.
In modern biology, remnants of this ancient world are still evident. For instance, ribosomes, the molecular machines that synthesize proteins in all living cells, are ribozymes themselves. This underscores the pivotal role RNA played in the evolutionary history of life on Earth.