Properties of Genetic Material (DNA versus RNA)

For any molecule to qualify as a cell's genetic material, it must satisfy three demanding properties, and this section compares how well DNA and RNA each measure up. The first property is self-replication: the molecule must be able to make faithful copies of itself, and both DNA and RNA satisfy this through the rule of complementary base pairing, which lets one strand serve as a template for building its partner strand; proteins, lacking any such templating mechanism, cannot self-replicate at all. The second property is stability: the genetic material must remain chemically and structurally unchanged across the different stages of an organism's life cycle. DNA is markedly more stable than RNA for a specific chemical reason -- every ribonucleotide in RNA carries a reactive hydroxyl (-OH) group at its 2' carbon that DNA's deoxyribose lacks, and this extra -OH group makes RNA far more chemically reactive and prone to spontaneous degradation; DNA's use of thymine instead of RNA's uracil adds a further layer of stability. Because DNA is double-stranded and the two strands are complementary, damaged or separated (denatured) DNA can often be repaired or can simply re-anneal (renature) once normal conditions return, a resilience RNA generally lacks. The third property is the ability to mutate, generating the variation that natural selection acts on; both DNA and RNA can mutate, but because RNA is inherently less stable, it accumulates mutations at a distinctly faster rate than DNA, which is exactly why RNA viruses, with their comparatively short life spans, tend to mutate and evolve much more quickly than DNA-based organisms. Finally, the genetic material must be able to express itself as observable, Mendelian characters: RNA can be translated into protein directly, so it can express traits without any intermediate step, whereas DNA always depends on RNA as an intermediary before a …