In order for evolution to occur, three different processes are required and must be met:
- 1. Generation of a diverse population
- 2. Selection of members based on criterion of fitness
- 3. Reproduction to enrich the population in more-fit members
Nucleic acids are such molecules that are capable of undergoing all three processes. Combinatorial chemistry is the concept of rapidly producing an abundant amount of a specific molecule of interest. Because of this process, diverse populations of nucleic acid molecules can be synthesized. A common example of this process involves attempting to create an RNA molecule that specifically binds ATP and other nucleotides. First, a randomized pool of RNA sequences, called apimers, are placed into an ATP affinity column. Some RNA molecules are then found bounded to ATP. These molcules are released from the affinity column by adding excess ATP. This collection of molecules are allowed to replicate into DNA by using the enzyme reverse transcriptase. Once transcribed into DNA, the molecules undergo PCR, and ultimately transcribe back into RNA.