Function isDNA

isDNA(nucleicAcid): nucleicAcid is DNA
Type guard for checking if a nucleic acid is DNA
Parameters
- nucleicAcid: NucleicAcid
  The nucleic acid to check
Returns nucleicAcid is DNA
True if the nucleic acid is DNA, false otherwise
Example
```
 //pass a DNA object
 isDNA(new DNA()); //returns true

 //pass an RNA object
 isDNA(new RNA()); //returns false
```
- Defined in src/utils/nucleic-acids.ts:79