* Viruses: Some viruses have DNA genomes (like herpesviruses), while others have RNA genomes (like influenza viruses). They do not contain both DNA and RNA.
* Certain organelles:
* Mitochondria: These organelles have their own DNA, but not RNA.
* Chloroplasts: These organelles have their own DNA, but not RNA.
* Artificial constructs: Scientists can create constructs containing only DNA or only RNA.
* Some prions: Prions are infectious proteins that can cause diseases like mad cow disease. They are composed of protein and do not contain any genetic material.
Important Note: Most living organisms contain both DNA and RNA. DNA is the blueprint for life, while RNA plays a crucial role in protein synthesis.
