Which statements describe notable exceptions to the central dogma of molecular biology?

Which statements describe notable exceptions to the central dogma of molecular biology?

• A. Retroviruses that reverse-transcribe RNA to DNA
• B. Bacteria reproduce by binary fission
• C. Eukaryotic nucleus functions
• D. Mitochondrial gene expression

Answer: (A)

Information typically flows from DNA to RNA to protein. The notable exception is reverse transcription, where RNA is used as a template to make DNA. Retroviruses carry an enzyme called reverse transcriptase that does exactly this, converting their RNA genome into DNA and often integrating that DNA into the host genome. Once the DNA is in the genome, cellular machinery can transcribe and translate it, so the original information has effectively taken an alternative route. The other statements don’t describe exceptions to this flow. Reproduction by binary fission is a growth and division process, not a reversal of information transfer. The functions of the eukaryotic nucleus pertain to where transcription and processing happen, not to reversing the direction of information transfer. Mitochondrial gene expression does involve transcription and translation, but it still follows the DNA -> RNA -> protein pathway, even though mitochondria have their own genome and some unique features.

Information typically flows from DNA to RNA to protein. The notable exception is reverse transcription, where RNA is used as a template to make DNA. Retroviruses carry an enzyme called reverse transcriptase that does exactly this, converting their RNA genome into DNA and often integrating that DNA into the host genome. Once the DNA is in the genome, cellular machinery can transcribe and translate it, so the original information has effectively taken an alternative route.

The other statements don’t describe exceptions to this flow. Reproduction by binary fission is a growth and division process, not a reversal of information transfer. The functions of the eukaryotic nucleus pertain to where transcription and processing happen, not to reversing the direction of information transfer. Mitochondrial gene expression does involve transcription and translation, but it still follows the DNA -> RNA -> protein pathway, even though mitochondria have their own genome and some unique features.