Which are exceptions to the central dogma?

Which are exceptions to the central dogma?

• A. DNA -> RNA only
• B. RNA -> Protein only
• C. Proteins store genetic information
• D. Reverse transcriptase and prions

Answer: (D)

The central idea being tested is that genetic information typically flows in one direction: from DNA to RNA to protein. An exception occurs when information moves backward, or when information is carried without nucleic acids at all. Reverse transcriptase shows this reverse flow: certain viruses (retroviruses) copy their RNA genome into DNA using the enzyme reverse transcriptase, and this DNA can integrate into the host genome. That means information can go from RNA back to DNA, not along the usual path. Prions demonstrate a different kind of exception. They are proteins that can propagate by changing normal proteins into the same misfolded form, without any RNA or DNA involved. This means heritable information can be carried and transmitted by protein conformation rather than nucleic acids. Together, these ideas—RNA to DNA copying and protein-only inheritance—illustrate exceptions to the standard central dogma, so the correct choice highlights reverse transcriptase and prions.

The central idea being tested is that genetic information typically flows in one direction: from DNA to RNA to protein. An exception occurs when information moves backward, or when information is carried without nucleic acids at all.

Reverse transcriptase shows this reverse flow: certain viruses (retroviruses) copy their RNA genome into DNA using the enzyme reverse transcriptase, and this DNA can integrate into the host genome. That means information can go from RNA back to DNA, not along the usual path.

Prions demonstrate a different kind of exception. They are proteins that can propagate by changing normal proteins into the same misfolded form, without any RNA or DNA involved. This means heritable information can be carried and transmitted by protein conformation rather than nucleic acids.

Together, these ideas—RNA to DNA copying and protein-only inheritance—illustrate exceptions to the standard central dogma, so the correct choice highlights reverse transcriptase and prions.