Central dogma in microbes In typical microbial cells, what is the usual direction of information flow according to the central dogma of molecular biology?

Introduction / Context:
The central dogma describes how genetic information is stored, expressed, and used. In bacteria and archaea, just like in eukaryotes, DNA serves as the heritable template, RNA as the transcript, and proteins as functional effectors. This question checks your recall of the canonical information flow.

Given Data / Assumptions:

• Standard cellular processes under non-specialized conditions.
• Ignoring special reverse-flow cases (e.g., reverse transcription, prions), unless explicitly stated.
• Focus on the usual, dominant pathway.

Concept / Approach:

DNA is replicated during cell division. Segments of DNA are transcribed into RNA, including mRNA. Ribosomes translate mRNA codons to synthesize polypeptides, which fold into active proteins. Therefore, the typical flow is DNA → RNA → protein.

Step-by-Step Solution:

Verification / Alternative check:

Genetic code universality and bacterial transcription/translation coupling affirm this standard flow in microbes.

Why Other Options Are Wrong:

• RNA → DNA → proteins: Reverse transcription first is not the usual case.
• Proteins → RNA → DNA or proteins → DNA → RNA: Proteins do not encode nucleic acid sequences.
• None of these: Incorrect because a standard pathway exists.

Common Pitfalls:

• Overgeneralizing special cases (retroviruses, reverse transcriptase) as the norm; they are exceptions.

Final Answer:

DNA → RNA → proteins