What are the exceptions to the general rule that DNA is the genetic material in all organisms? What evidence supports these exceptions?

Key Concepts

DNA as Genetic Material

DNA (deoxyribonucleic acid) is the primary carrier of genetic information in most organisms, encoding the instructions for development, functioning, and reproduction. The central dogma of molecular biology describes the flow of genetic information from DNA to RNA to protein, establishing DNA's role as the fundamental genetic material in cells.

Exceptions to DNA as Genetic Material

While DNA is the genetic material in most organisms, there are notable exceptions, such as certain viruses that use RNA (ribonucleic acid) instead. These RNA viruses, including retroviruses like HIV, utilize RNA to store genetic information and can even reverse transcribe their RNA into DNA within host cells, challenging the traditional view of DNA as the sole genetic material.

Evidence Supporting Exceptions

Evidence for RNA as genetic material comes from studies of various viruses and their replication mechanisms. For instance, the discovery of retroviruses demonstrated that RNA can serve as a template for DNA synthesis, while experiments with tobacco mosaic virus showed that RNA alone could infect host plants, providing clear examples of RNA functioning as genetic material.