● The debate between proteins versus `color{Violet}"DNA as the genetic material"` was unequivocally resolved from `color{Violet}"Hershey-Chase"` experiment.

● It became an established fact that it is `color{Violet}"DNA"` that acts as genetic material.

● However, it subsequently became clear that in some `color{Violet}"viruses"`, `color{Violet}"RNA"` is the `color{Violet}"genetic material"` (for example, Tobacco Mosaic viruses, QB bacteriophage, etc.).

● A molecule that can act as a genetic material must fulfill the following criteria:

`star` It should be able to `color{Violet}"generate its replica"` (`color{Violet}"Replication"`).

`star` It should `color{Violet}"chemically"` and `color{Violet}"structurally"` be `color{Violet}"stable"`.

`star` It should provide the scope for `color{Violet}"slow changes"` (`color{Violet}"mutation"`) that are required for `color{Violet}"evolution"`.

`star` It should be able to `color{Violet}"express itself"` in the form of `color{Violet}"Mendelian Characters"`.

● If one examines each requirement one by one, because of rule of `color{Violet}"base pairing and complementarity"`, both the nucleic acids (DNA and RNA) have the ability to direct their duplications.

● The other molecules in the living system, such as `color{Violet}"proteins fail to fulfill"` first criteria itself.

● The genetic material should be `color{Violet}"stable enough"` not to change with different `color{Violet}"stages of life cycle"`, age or with change in physiology of the organism.

● Stability as one of the properties of genetic material was very evident in `color{Violet}"Griffith’s ‘transforming principle’"`itself that `color{Violet}"heat"`, which killed the bacteria, at least did not destroy some of the properties of genetic material.

● This now can easily be explained in light of the DNA that the `color{Violet}"two strands"` being `color{Violet}"complementary"` if separated by heating `color{Violet}"come together"`, when appropriate conditions are provided.

● Further, `color{Violet}"2'-OH group"` present at every nucleotide in RNA is a `color{Violet}"reactive group"` and makes `color{Violet}"RNA labile"` and easily degradable.

● RNA is also now known to be `color{Violet}"catalytic"`, hence `color{Violet}"reactive"`.

● Therefore, DNA chemically is `color{Violet}"less reactive"` and `color{Violet}"structurally more stable"` when compared to RNA.

● Therefore, among the two nucleic acids, the `color{brown}"DNA is a better"` `color{brown}"genetic material"`.

● In fact, the presence of `color{Violet}"thymine"` at the `color{Violet}"place of uracil"` also confers `color{Violet}"additional stability"` to DNA.

● Both `color{Violet}"DNA and RNA"` are able to `color{Violet}"mutate"`.

● In fact, `color{Violet}"RNA being unstable"`, mutate at a `color{Violet}"faster rate"`.

● Consequently, `color{Violet}"viruses"` having RNA genome and having `color{Violet}"shorter life span"` `color{Violet}"mutate"` and `color{Violet}"evolve faster."`

● RNA can `color{Violet}"directly code"` for the synthesis of proteins, hence can `color{Violet}"easily express"` the characters.

● DNA, however, is dependent on RNA for synthesis of proteins.

● The `color{Violet}"protein synthesising machinery"` has evolved around RNA.

● The above discussion indicate that both `color{Violet}"RNA and DNA"` can function as `color{Violet}"genetic material"`, but DNA being `color{Violet}"more stable"` is preferred for `color{Violet}"storage"` of `color{Violet}"genetic information"`.

● For the `color{Violet}"transmission"` of genetic information, `color{Violet}"RNA is better."`

● `color{brown}"RNA was the"` `color{brown}"first genetic material"`.

● There is now enough evidence to suggest that `color{violet}"essential life processes"` (such as metabolism, translation, splicing, etc.), `color{violet}"evolved around RNA"`.

● RNA used to act as a `color{violet}"genetic material"` as well as a `color{violet}"catalyst"` (there are some important biochemical reactions in living systems that are catalysed by RNA catalysts and not by protein enzymes).

● But, `color{violet}"RNA being a catalyst"` was `color{violet}"reactive"` and hence `color{violet}"unstable"`.

● Therefore, DNA has `color{violet}"evolved"` from RNA with `color{violet}"chemical modifications"` that make it more stable.

● DNA being `color{violet}"double stranded"` and having `color{violet}"complementary strand"` further `color{violet}"resists changes"` by evolving a process of `color{violet}"repair"`.